I'm not optimistic about the future of the MacBook Air, which is unfortunate because for what it is, it's a solid machine.
That said, yeah, as someone said earlier, if you want a Retina display, go with a 13" Pro. The only other differences between a (retina) 13" Pro and a 13" Air are higher clock speeds on the Pro, a slightly thicker profile (and with it, a near negligible weight difference), support for 16GB of RAM and better graphics. If you need one of these features, there's no reason to not get all of them.
So, no, I don't think think there will be a retina version of the MacBook Air. They'll get 16GB of RAM when the chipset they use starts supporting it. For everything else, it's helpful to remember that this machine is positioned to be the modern-day version of the polycarbonate MacBooks of old and soon, Apple will position the machine currently titled MacBook to replace it, much like the MacBook Air did with the machine previously titled "MacBook". Both systems were, for their respective times, Apple's vision of the consumer laptop. Apple doesn't believe we need ports, the philosophy that we had with the MacBook Air when it first came out and they reiterate that now with the MacBook. History is repeating.
Right now I see Apple's whole computer lineup about to hit a big transition. Other than the new rMB, every computer line, both laptops and desktops, have not had a redesign in at least 2 or 3 years (redesign defined as a new chassis, not just upgraded components). Additionally, USB-C as a physical connector is showing up on lots of non-Apple equipment, which means it is gaining traction, along with Thunderbolt 3. We haven't seen a lot of Skylake processors applied to any of Apple's computers yet: the 27" iMac is the only one that's got it so far. While it's been a long wait, I think we'll see some significant changes across the board this spring and/or at WWDC.
That said, I agree that MBA's days are numbered due to the new rMB. Skylake in the rMB will pretty much give it the extra power it needs to get it close to where the MBA is now. I think Apple will release a 14" rMB as well as a lower end 12" rMB (4GB RAM and 128GB SSD) for their $1K price point. This new rMB lineup will replace the MBA, which Apple might keep around for another year for those who want one, just as the non-retina MBP hung around for a while. Since the MBP is due for a redesign, it's not hard to see new 14" and 16" MBP that replace the current 13 and 15" models but remain about the same size. USB-C/Thunderbolt 3 across the board as well, with maybe a single USB-A port for legacy connectivity.
We'll know in 4 or 5 months how it all pans out, but that's my guess at the moment.