The thing is Apple and Intel have always had a very close relationship and the current MacBook Air processors were customized specifically for the Air... this time around they don't have that relationship and none of the current processors fit the bill.
I can see where you are coming from in regards to the processors though. I can see it going either way - decreasing the performance in favor of battery life and lowering the prices, or having the price stay the same but throwing in a i7/high end i5 and getting more heat/less battery but better performance.
The ATI 5xxx graphics smoke the floor with any nVidia equivalents, and from what I know, they use less energy. The only thing nVidia has going for it is the switchable stuff, but I think most consumers would rather have a better graphics card on all the time with the energy/output inbetween that of an Intel HD graphics and nVidia 310M. I don't want to speak for all consumers though so correct me if I'm wrong.
Actually, it was the original MBA that had its own "custom" Intel processor. Many other notebooks use SL9x00 CPUs, including Dell's own ultraportable competitor to the MBA, Adamo.
I wouldn't put it past Apple to get a custom CPU, maybe even less the IGP 45nm DIE. Don't count on the relationship to be down, because I believe Nvidia lost its license due to the appearance of Apple selecting it over Intel's own chipsets. Intel wants to be inside of the Mac computers for the money and the branding. Apple buying Nvidia over Intel was the start of the end of Nvidia's license. Intel will definitely bend over backwards to get into every premium or pro Mac, and I don't think it's beyond removing a 45 nm GMA DIE to get it.
Let me clarify, the i5 is NOT a high-end CPU in any way, shape or form. It's nearly $100 less than the current C2D TRUELY high-end SL9600 CPU. If Apple wants to decrease performance, it will obviously use the Core i7-6x0UM an ultra low voltage CPU. Apple would much prefer 4 MB L3 cache and a far superior HD graphics experience. The i5 is where people think a mid-grade computer should be, but Apple has never gone cheap on the MBA... it's done miniaturized but not cheap. In fact, the Core i7-6x0LM CPUs that Intel scheduled to replace the current MBA's C2D SL9x00 Penryn CPUs are about $15 cheaper than the current SL9x00s.
The simple truth is the Core i7 makes far more sense than the Core i5 in ultra low voltage form. Go look, and both CPUs are already available for Apple in Core i7 CPUs. The Core i5 you're hopeful for doesn't even match the current Core i7 CPUs that are ultra low voltage and available right now. This is not to say Apple will not stick with the LOW VOLTAGE CPUs where it's currently positioned in the MBA.
The reason the MBA is pure perfection is the 6 MB L2 cache, and clock speed performance while using low voltage. It gives the MBA a truly better experience than one would expect and similar to the MB. It does that by taking advantage of the cache because it's not as fast as the 35W TDP MB CPUs but uses less power able to cool it down in such a thin case with limited cooling space. It also uses an Nvidia GPU and an SSD to make the MBA literally faster than a MB for those willing to pay for it.
Both Intel and Apple will want the MBA branded as a Core i7 CPU. Most people don't even know the differences and think Core i7 means quad core or something more powerful. The Core i7 brand offers the 640LM and 620LM which are the Intel branded replacements for the current MBA's low voltage SL9x00 series. We have zero reason to believe Apple wouldn't continue on with a low voltage CPU. If Apple went ultra low voltage, it would possibly be to make a dedicated graphics card to work inside of it. However, with hybrid tech that's even less important as the dedicated GPU will only be used as needed.
If Apple wants to go ultra low voltage, the Core i7-640UM and i7-620UM are already available and both offer superior performance, and more importantly more L3 Cache and double the performance from the GPU built in. If Apple doesn't use a secondary discrete card, it would be absolutely STUPID for it to use an i5 CPU. The i5 is going to have 60% of the standard graphics performance of the i7, half the L3 cache of the i7, and ALL AT THE SAME ULTRA LOW VOLTAGE 18W. Why would Apple be that stupid? It just doesn't add up. I believe you're not clarifying where Apple already is with the MBA and where it's definitely going with the MBA.
Again, if Apple didn't have the iPad positioned as the lower cost secondary entertainment/web netbook replacement device, maybe the MBA would take the position of further removing its capabilities to get it into a cheaper price point. Why should Apple lower the price point from where it's already at? Why would it want to sell MBAs for $1300? Why wouldn't it want to keep the prices up and do it by taking advantage of both the branding and performance gains of the Core i7 over the Core i5? We haven't even touched the fact that there are no "LOW VOLTAGE" Core i5 CPUs available... where and why would Apple move away from Low Voltage? How could it do it with a Core i5? It couldn't not now... not until late this year, and not without a massive performance loss in GPU capabilities of the built-in graphics.
I will gladly put $100 on the line that is on a Core i7-6x0LM or i7-6x0UM over any of your Core i5 CPUs, current or future. Apple simply cannot go backwards with the MBA, and that's exactly where it would be going with a Core i5 ultra low voltage... far backwards from the current CPUs. We would all be better off buying a C2D MBA... and Apple would be better off keeping a C2D in the MBA and simply adding 4 GB of RAM to it. I will be done with the MBA if I have to have that worthless Core i5 ultra low voltage CPU in my MBA... on I will be to better things whether it be an "Airized" MBP or something else (like the Vaio Z where I could be very easily - I just need Apple to prove it the wrong choice, but another Tuesday without an update).
I agree the ATI 5XXX will smoke the Nvidia 310m, but this is Apple we're talking about. MBP buyers will be lucky to get the ATI 5450; they all want the 5870 and are saying they will settle for the 5830, but I will laugh my ass off when they get the Nvidia 330 GT or ATI 5450.
In all truth, I don't see Apple using ATI even though they offer faster graphics solutions. Apple is more into energy savings and yet offering the best overall value for complete system performance... The MBA will be lucky to get a 310m. If it were to get a 330 GT, it would probably have to use the ultra low voltage CPUs... but even then I don't know.
With Optimus, Apple gets exactly what it wants. A fair card that can perform in the low to low-mid range areas depending on dedicated card used in which Mac, and yet the energy savings the majority of the time when using the Intel IGP. I guess it's completely possible that ATI allows Apple to introduce a new tech from ATI in the new Mac notebooks. I just don't see Apple using any high end graphics - not even as high end as the 5450. And truthfully, most of us would be much better off with C2D and Nvidia chipsets anyways.
There are different groups getting into gaming on Macs, and that's why Apple should develop another series of notebooks focusing on high-end graphics cards and large displays, and lose the other features focused on other Mac notebooks not necessary to them. There is a whole range of people not being catered to by Apple, and I see it as a missed opportunity whether it's a headless Mac, a netbook, a gaming desktop, or a gaming notebook - they're all missed opportunities that Apple's is not capitalizing on. It makes me wonder if Apple has something up its sleeve and working with Steam to introduce computers more capable... no clues here and not truly speculating, just a thought that probably means nothing.
If I had to bet on the next MBA right now... Core i7-620LM, Intel IGP only, 2 GB RAM, 128 GB SSD for $1599. Core i7-640LM, Nvidia 310m 256 MB dedicated w/Optimus, 4 GB RAM, 256 GB SSD, a new display tech - $1999. Both get better speakers, glass trackpads, and USB 3.0. If we get better tech than these, I can see higher prices. I also see BTO options coming back to the MBA. Hopefully a $500 upgrade to 8 GB RAM. Maybe a Core i7 LM over a UM for more money, or a dedicated graphics card versus only Intel's GMA IGP. Maybe other things too, like the HD/IPS display I am expecting.
What I don't fear because it isn't happening... Core i5-xxxUM, 1.06/1.2 GHz, Intel or other graphics, and any other add you want.
OMG, what a waste of my time... nobody will even read this lengthy post!