This report filed on Friday is a pretty good read looking at the online future for console systems and if there really even is one. There are quotes and discussion from reps for Sony Microsoft and Nintendo. Both Sony and Microsoft have run into issues with trying to get their machines online and working with broadband having changed their strategies and Nintendo has opted to not ship with online capabilities but use a follow-up release.

Sony Corp the market-share leader with its PlayStation series, envisions its consoles becoming all-in-one consumer entertainment systems, complete with the ability to play movies, music and browse the Web.
[...] and MS:
``We've designed Xbox to be a great online platform out of the box,'' said Robbie Bach, the top executive in charge of Microsoft's Xbox and gaming division. ``We don't think it makes sense for you to have to go out and buy a lot of components.''

I dont really see any of the three machines really making a big impact online right away. If one of the machines comes out with a Diablo port though you'll see a hell of a lot of people signing up. Would be interesting to see Blizzard try and patch a GameCube or PS2 game though :)