The "Air" name does not make sense anymore unless you put it on the 12" MacBook. A redesigned Air would not be thinner (processors with cooling being the key difference) than the MacBook. I actually think there will be so much overlap with the new MacBook Pro line that the MacBook lineup can be brought down to this:
(13)14" MacBook Pro
(15)16" MacBook Pro
Having used the 12" MacBook for a week now I strongly believe there is no need for another laptop that's just aimed for basic tasks. It handles everything perfectly (low-end 2015 model). Just this and Pro models will do.
Air`s dead in the water, Apple already updated the 13" Air will be discontinued soon as Apple can increase profitability of the Retina MacBook to the same levels. Is very obvious that development of the Air has ceased, little like USB A on the current rMBP, it will be gone on the next revision, like it or loath it...
If the Macbook Air 13" really gets redesigned plus a retina screen during WWDC, I don't think there is any point of buying the retina Macbook now...
Another deal breaker for MBA is the massive bezelsIt's all a bit sad. For me the MBA is more than portable enough. The grams I would save with a Macbook offers me close to 0 value. The MBA is powerful enough - I rarely need what a Pro would offer. I'm sure "portless" will be the future, but for the moment I value a couple of extra ports. A dongle to charge and use external monitor at the same time is not acceptable.
So why not just get a MBA? I hate the screen. If I hadn't spilled milk on my 2012 I wouldn't have been looking for a replacement, but now I got nothing but my work computer.
A retina MBA would be pretty perfect for a lot of people in my opinion. More suited to offer a great all round portable computer with the current battery, cpu etc. technology than the current Macbook. Unfortunately I don't think it will happen.
Another deal breaker for MBA is the massive bezels
I know a lot of people have been clamoring for a retina MBA for years, however I think the answer is pretty clear as to why Apple didn't release one. Apple focused on battery life more than anything else in recent years in MBA updates and it's made it the easiest to recommend laptop for a lot of people, even still. My father, for example, could give a crap about what screen resolution he had. The MBA is still the best recommendation for him with the combo of battery life, solid construction, keyboard/trackpad, price and durability. Apple clearly felt they couldn't release a MBA with a retina screen that offered a comparable experience in the battery department. Battery life is the bottleneck in this scenario, as is the case with many Apple products.
If you have wanted a retina MBA all this time, that's what the 13'' rMBP has been. Very similar in a lot of ways and an awesome screen. That device represents the best combo of battery life/screen quality Apple was able to produce in 2012, hence why there was never a retina MBA. Looking forward, there's no reason for Apple to release a new 'Air' model. For one, the 'Air' moniker makes no sense anymore given the 'Macbook' is now the thinnest/lightest notebook Apple makes; that's not changing at WWDC either. Given more recent purchasing patterns indicating consumers nowadays are waiting longer and longer to upgrade their laptops, it makes sense for Apple to simplify their notebook product line into two camps. Macbook Pros, and Macbooks.
My prediction is that in 2017, Apple will release a 14'' rMB. It will essentially be the new 13'' Air. By this time, Kaby Lake will have arrived in these machines and they'll support TB3/USB-C natively. They'll throw 2 ports on this one to silence the haters and call it a day. It will share the design aspects of the rMB with a larger body. Again, critics will condemn the device for no connectivity options, and consumers will vote with their wallets. Expect a nearly bezel-less 14'' rMB that's thinner and has a similar footprint to the 13'' MBA. It'll sell like hotcakes.
I believe all this time, the needs for most computer users have been so simple. The GHz wars in the 90's and 2000's, along with strong advertising from Intel, brainwashed consumers into thinking that they needed highly-clocked processors. This still remains true to this day. In reality, I'd argue the large majority of users have never needed more than MS Office, iTunes, a good browser, and a few non-resource intensive applications. Even many business folks fall under this classification for their work machines. The current rMB can handle these tasks with complete ease and I only expect this to become more true as Kaby Lake makes its way in. The true 'new' Apple Macbook Air will be the 14'' rMB.