Car buying guide similar to Buyer's Guide of MacRumors?

just pick a model youre interested in and google for upcoming refreshes/redesigns, etc

The Inside Line forums on Edmunds have a section called future vehicles, I believe.

http://acurazine.com/forums/automotive-news-6/

These guys keep up with automotive news and have a huge archive. I know it says "Acurazine", but their news page isn't site specific really.

Not aware of any sites that contain information you're looking for (there's just too much to keep up on), but your best bet is go to a forum of a car you're interested in and use their resources.

http://www.caranddriver.com/list-news-future-cars

http://www.motortrend.com/future/