From a technological and pricing point of view that would be the logical i7 option for a Rev D MBA.
From a marketing point of view I'd say: hmmmm...
They'd have to advert with a slower bus speed and similar processor speeds. That is two bonus points for reasons to buy less. And in Apple tradition marketing decisions often outweigh technical sense.
A much better battery could make the i7-6x0LM an option, but it would probably also make the MBA more expensive than it is now...
Juts thinking out loud...
Wait...edit. Just thinking about the heat the LM would produce compared to the UM...I am inclined to agree with you!
But you're still not factoring in that the Core i7-6x0LM is the Low Voltage CPU that REPLACES the Core 2 Duo Penryn SL9x00 CPUs that are already in the MBA. In addition, the Core i7-6x0LM is ACTUALLY LESS EXPENSIVE than the SL9x00 CPUs - by about $15 each. Again, the MBA uses an expensive CPU with double the cache of the MB and 13" MBP CPUs. Apple really hit a winner with the SL9x00 CPUs.
The thing is they throttle when are heated up... so like I said before the Core i7-6x0UM (ultra low voltage) provides a similar experience to the current SL9x00 CPUs since the SL9x00 is throttled. I wonder if Apple wouldn't just put "Boost to 2.13 and 2.26 GHz instead of marketing the lower clock speed." It was even a big deal when the 2.13 GHz was released and it was reported that the 2.13 performed at a lower percentage of clock speed. Remember that it was throttling down to 1.6 GHz just as the 1.86 GHz CPU, and that led to similar results when throttled.
Bottom line is Apple is going with either another C2D CPU or a Core i7 CPU (with very rare possibility of one Core i5 CPU that would work but not optimal). It is not going to use a Core i3 CPU, and people that say that simply have no clue about the Core i-series CPUs. Most people just assume that the Core i3 is low end, so that's what Apple would use... but Apple NEVER used an inexpensive CPU in the MBA. Where Apple has really spent money on the MBA has been the CPU. The Intel Core system really has people confused, and most people think Core i7 means quad core (because iMac uses a Core i7 that's quad core), but that's not true either. People just don't know about the CPUs, but in five minutes anyone can go figure it out - Intel's site shows exactly how the CPUs work.
Arrandale Mobile CPUs...
Core i3
doesn't boost to higher clock speed, and they're all 35W TDP CPUs - could be used in a WhiteBook or even 13" MBP. They are dual core, Hyper-Thread, and have 3 MB Cache.
Core i5
does boost to higher clock speed, and had both 35W TDP and 18W TDP (ultra low voltage) CPUs - could be used in mid range MBPs. Possible but doubtful for MBA. They are dual core, Hyper-Thread, and have 3 MB Cache.
Core i7
does boost to higher clock speed,
offers faster clock speed variants than Core i5, and has (45W TDP not Arrandale), 35W TDP, 25W TDP, and 18W TDP CPUs - 35W TDP could be used in MBP and 25W TDP could be used in MBA (with possibility of 18W TDP ultra low voltage). The Core i7 has both dual core 32nm Arrandale CPUs (and two quad core not Arrandale 45nm CPUs). These Arrandale CPUs are dual core, Hyper-Thread, and have 4 MB L3 Cache. The advantages of Arrandale Core i7 over Core i5 are more L3 Cache and faster clock speeds from same TDP.
http://www.intel.com/products/processor/index.htm
So Core i7 doesn't mean quad core, which is confusing to many because the desktop Core i5/i7 used in the iMac is quad core. And the quad core i7 available isn't an Arrandale CPU and has significantly lower clock speeds than the Mac notebooks have. In addition, Apple uses 35W TDP in its MBs and MBP. A 45W TDP Core i7 quad core CPU would probably be too hot for an MBP.