Instruction sets?? What will the future bring

Alright, so i admit that this is kind of a Intel vs. AMD post. But i want the heart of this topic to be on the instruction sets supported within each CPU core, since currently the two processors are neck and neck (with the P4 2.2ghz and the Athlon XP 2000+)
From what i understand Athlon XP supports MMX, Enhanced 3D now!, 3D Now! Professional, and SSE. But the P4 only supports MMX, SSE, and SSE2
Completely forgetting about upcoming advances like the Athlon Hammer and P4's RDRAM upgrade (at a huge cost) does anyone know to what degree all these instruction sets come into play. I know i've heard about MMX and SSE being used... certain programs for benchmarking test it (forget which ones). But what about the 3D Now!'s - i hear very little about them and what programs use those instructions... and now with this whole new SSE2 set, what programs are gonna use that?? And why on earth hasn't P4 added the 3D now's, it just seems like a small thing you can do to prevent the other company from taking your title...
Alright, i'm getting a head ache. Really, i just want to know how i can find out what programs (Games to Office) use these instruction sets so that i can chose a processor upgrade that will last, and by that i mean, i won't need to upgrade again for atleast 2 years. A big order to fill i know, but hey, i can't be the only one asking these questions.
Personally, i want the Hammer core for price, features and completeness of coding... and frankily, the over heating of the AMD processors, though it stinks, i can deal with and compensate for.
Hey, this looks like a good spot to stop before i ramble my point away.