If I had to make a bet I would say yes, next year there will be Retina Airs. Thought they may have this year, except they wanted to keep the Retina spotlight on the Macbook Pro. Apple is clever at marketing so for them to release it on the Air would have taken some of the focus away.
Instead they gave a few reasonable boosts to the performance that while nice, and somewhat tempting, unfortunately for me don't warrant an upgrade. I was really hoping it would, but it doesn't.
Having the new iPad sitting next to my Mac Air, the screen difference is large. My Air now looks a little fuzzy, while the iPad shines. Thinking about it now I would say for sure that Apple would be crazy not to update the Air's screen to retina level next year. While everything else is getting the treatment it just makes logical sense.
As someone mentioned before if you really need it now, you'd better get it now and you won't be disappointed. If it is not a priority, then wait for the retina Macbook Air coming out next year.
The Air is a key product for Apple, so while the iPhone, iPad and now Macbook Pro all receive retina, they won't want to leave the Air behind for long. Well I could be wrong, maybe I am being hopeful at least, but still it would seem logical that thats what will happen.