As long as you can still buy balsa, glue, and servos there will be plenty of opportunities to keep building. There are (quite literally) thousands of plans available to download and just about any kind of hardware you can think of is just a mouse-click away.

So while I will definitely miss those Top Flite kits too, their absence from the market won't stop me from building (the stash of kits I have been collecting these last few years won't hurt either )