Joel in his Strategy Letter IV has to say the following about the future of web applications:

What’s going to happen? The winners are going to do what worked at Bell Labs in 1978: build a programming language, like C, that’s portable and efficient. It should compile down to “native” code (native code being JavaScript and DOMs) with different backends for different target platforms, where the compiler writers obsess about performance so you don’t have to. It’ll have all the same performance as native JavaScript with full access to the DOM in a consistent fashion, and it’ll compile down to IE native and Firefox native portably and automatically. And, yes, it’ll go into your CSS and muck around with it in some frightening but provably-correct way so you never have to think about CSS incompatibilities ever again. Ever. Oh joyous day that will be.

Good to see that other visionaries have the same vision, too :-)