I seriously doubt they'll do a complete redesign of the Air in 1.5 years. The market for these is so much smaller than for MB and even MBP since it's quite a compromise and I doubt most people use it as their primary machine. White MB took over 3 years for a severe redesign (mid 2006 - late 2009) while MBP took over 2 (mid 2006 - late 2008) so investing lots of money into a redesign of a machine that's not a huge seller/money maker after such a short design lifespan doesn't make any sense. On other hand, it's Apple who has major money so any predictions are moot at best. But I'm betting it will be an incremental update again with more RAM, larger drive and CPU speed bump (pick any two).
What I don't understand is why people purchase brand new machines. If warranty is a major concern, why doesn't the OP just buy a refurbished one that comes with same one year warranty as the new one? Or just buy a machine that's less than 1 year old and still has original Apple warranty left and purchase additional Applecare for 2 years. Either way, you get to save a bundle and you end up with a good machine that still has warranty. And if you sell it down the road without warranty it's still worth about same as any revision C Air, no matter when it was bought.
What I don't understand is why people purchase brand new machines. If warranty is a major concern, why doesn't the OP just buy a refurbished one that comes with same one year warranty as the new one? Or just buy a machine that's less than 1 year old and still has original Apple warranty left and purchase additional Applecare for 2 years. Either way, you get to save a bundle and you end up with a good machine that still has warranty. And if you sell it down the road without warranty it's still worth about same as any revision C Air, no matter when it was bought.