To help TheSource getting his 30 predictions (love your writings) I'll add mine and thereby have my first post:
Lowest total market (no killer machine like PS2 this gen): 130 M
Wii: 70 M
(first year incredible: next 2 years should see a lot of great (3rd party) games, after that maybe declining sales)
PS3: 35 M
(bad start, but great games coming, probably longest lifespan + Japanese support)
X360: 25 M (No Japanese support, struggeling over past months, same market as Xbox)