I'm a little disappointed ...
When I read the thread title I immediately thought that a hacker had ported the Wii emulator to the PS3; and I'm surprised this hasn't happened yet. While the XBox 360 and PS3 are not powerful enough to emulate a system that is as powerful as the Wii and has a vastly different architecture to the XBox 360 and PS3, being that the XBox 360, PS3 and Wii all have PowerPC based CPUs (and I believe that the additional instructions added into the Gamecube's Power3 CPU were included in most later core designs) I would think that it would be possible to emulate the Wii on the HD consoles.