Having read your post, I'm curious as to why you wish to get an Air.
At the moment, there are two great reasons for buying an Air; uber-portability, and excellent battery life (in the 2013 models).
Of course, the retina screen is nicer than the current MBA screen, and, no, I have absolutely no idea when Apple will add the retina screen to the MBA line-up, but, I expect it to happen sometime over the next few years.
For me, retina - while really good - is not a deal breaker, whereas speed, portability and excellent battery life all are.
Re your situation, if you need a computer (or if your old one is showing signs of increasing age - i.e. many beach balls are making an appearance, when you attempt even a mundane and relatively undemanding action), buy one; if, however, you merely want one, perhaps you should wait until there has been a more radical update.
And, re actual purchases: I doubt you'll go far wrong with a refurb; you will get a fairly generous discount, along with a full warranty.
Whatever you decide, the very best of luck with it.