PPC is still alive and really alive, and it can match x86 computing power, look to the PS3 powerful and cheap, so we don't need to shift to ARM or whatever.
The PS3 is hardly powerful, for general computing it's a joke and not even a good joke. Example of Blender render times:
http://eofw.org/bench/You'll find a couple PS3 "systems" listed in the very bottom, the fastest:
3431
00:06:31.39 1x Sony PlayStation 3 IBM Cell 3000MHz 1 Cell Broadband 512MB Linux Ubuntu 2.44 test.blend Using Ubuntu on my Playstation 3. 2007-07-25 23:09:50
Compare to generic run-of-the-mill PC available at about the same price as PS3:
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00:00:28.60 1x Intel® Core™2Quad Q6600 2400MHz 3381MHz 4 p35 4096MB WinXP Pro 2.45 test.blend 24/7 setup 2007-11-01 17:16:45