Anybody think that maybe either AMD Intel or Nvidia might potentially enter the console market themselves at some point?

Nope. They do however provide custom hardware for the major console developers.

PS3 uses nvidia, 360 uses AMD for gfx card

No need to put those 2 companies in the console market seeing how they supply the consoles the video card. If they were to compete, they lose profit, not gain.

um they do... its called the personal computer console pcc for short