Though this is old news by now, here's a link at eWeek that talks about IBM's new processor and how Apple might put it to use. Here's a semi-key quote:

[The new processor] will also support Vector/SIMD Multimedia Extensions (VMX), a group of 162 instructions that speed data processing and algorithmic-intensive tasks, such as multimedia creation and display.

Sources note that internal documents and publicly released information make no explicit mention of Motorola's Altivec multimedia extensions currently used in the PowerPC G4 and marketed under the name Velocity Engine by Apple. However, they said that VMX and Altivec are highly compatible, if not identical.

I'm probably over-estimating its value, but I think AltiVec is the one big reason Apple won't be moving towards x86 architecture anytime soon. I have to imagine most of the iApps that deal with video are heavily tuned to use the AltiVec instruction set, and I wonder how much trouble and retesting it'd be to set these apps back up with x86 and their extended instruction sets "for multimedia". Same thing for Photoshop on OS X, the one arena where, with a few filters, Apple was able to rig up tests so that, thanks in large part to AltiVec, they could actually win.

Here's another key quote that, if true, might be more reason not to think Apple's going to go the convluted route of x86 (where they'd have to dream up something new to keep the hardware proprietary as well)...

Sources said that benchmarks and applications tests demonstrate that a 1GHz [new] processor doubles the performance of the 1GHz Motorola PowerPC G4 processor in current Macs. Even so, they said, the first run on [new] processors should range from 1.4 to 2GHz, depending on yield.

But whaddya I know? :^)