It's the OS that mostly effects what programs can and can't run, going to an X86 platform you wont be able to run anymore than you could on the PPC platform because it will still be running a MacOS.
There are 2 reasons Apple is going to x86 (and they've both been covered).
1. the X86 architecture is less power hungry and works better with laptops
2. the CELL is the next chip-set after the current PPC G5 and Apple was disappointed with it. so rather than use the IBM CELL they're going to Intel Pentiums.