I will just go over the top. Anyone who disagrees feel free to leave a comment, I will assume the rest of the internet thinks I am Kreskin.
Wii
They will sell about 22 million consoles, putting them at 40.5 million lifetime. Increases in production won't come early enough to push out more and shortages will still be seen in early and late 2008 specifically in the US. No pricedrop. Japan will see new colors. US will see a new SKU that packs in WiiFit.
Mario Galaxy will sell an additional 3.5 million copies, topping 7 million lifetime. Smash Bros. and MarioKart will both sell 6 million copies. Wii will get a ton of RPGs from 3rd parties. Kingdom Hearts 3 will be annouced for Wii. Animal Crossing will get delayed to 2009.
PS3
Sales will start to rebound, specifically in Europe. Selling about 13 million consoles bringing their total to 22 million. Complete PS2 software emulation will be developed allowing backwards compatibility to be added to the 40GB. Sony will be forced to drop prices $50 after Microsoft drops prices. New red color available in Japan.
GT5 and Final Fantasy XIII won't be released until 2009. Little Big Planet will be a critical success but sell very poorly under 500,000. Kilzone 2 will stink it up but still sell over 1 million. Metal Gear Solid 4 will be massive and stay exclusive pushing hardware and selling over 3 million in 2008. GTA4 will outsell 360 version in Europe and Japan but not in the US, 3 million total. Devil May Cry 4 2 million.
360
About 7 million were sold in 2006 and 2007. Without Halo 3 launch I say 6.5 million in 2008 putting it at 22.5 million. Despite quality software it is largely seen as it's last big year for the 360. It will continue to be dead in Japan and basically die in Europe now the the PS3 has found its legs. A price drop to $349, $299, $249 before GTA4 will be seen as not enough. Leaked details of next Xbox start to surface, eta 2010.
GTA4 will sell 4 million, Halo Wars will sell 2 million, Gears of War 2 will sell 2 million. Fable 2 2 million. No games in new franchises will sell over 1 million.
Final* Word on Game Delays:
The game will not be any better or include more content then planned. Any commnets that say so are just PR hogwash to make you feel better for having to wait.
Delays are due to lack of proper resources, skill, or adequate planning by the developer.
Do be thankful that they have enough respect for you to delay the game and maintain its intended level of quality.
*naznatips is exempt