Here are some of the games I have heard of:
1. Killer Instinct 3:
Rare has been working on 2 secret games for quite some time, I would assume that this is one. KI 2 was probably one of my favorite fighting games as a kid so I would be looking forward to this.
http://www.xbox360fanboy.com/2006/12/29/rumor-killer-instinct-3-for-360-in-2007/
http://features.teamxbox.com/xbox/1464/Most-Wanted-Unannounced-Xbox-360-Games/p2/
2. Mech Assault 3:
Didnt like the first two but none the less this is to be in development.
http://features.teamxbox.com/xbox/1464/Most-Wanted-Unannounced-Xbox-360-Games/p8/
3. Jade Empire 2:
The first one was great I thought. I found it to be short even if you do the side quests but none the less a great game. Seeing the BioWare is probably busy with ME2, I wonder if this is still on the plate.
http://kotaku.com/339062/jade-empire-2-in-development-at-bioware
4.KOTOR 3:
Probably a top 3 game for the orginal xbox again, I find it hard to believe that BioWare is doing this in addition to ME2 and JE2 (If it is in development).
http://www.computerandvideogames.com/article.php?id=165554
5. GoldenEye
A classic and in my opinion defined FPS's. This has been rumored for quite some time so I wouldnt be surprised if it came to XBLA.
http://www.wikixbox360.com/page/Goldeneye+64+coming+to+Xbox+Live+Arcade%3F?t=anon
6. Spore
Big PC release this year and has been hinted as to coming to the 360. I am probably getting it for the PC anayways but it should be in here.
http://www.eurogamer.net/article.php?article_id=59423
7. Crysis
Already confirmed? I havent heard much about this but again wouldnt be surprised as MS published it.
http://digg.com/gaming_news/Crysis_Confirmed_For_Xbox_360
8. Diablo 3
Far feched and I would only buy it for the PC anyways but it has been rumored.
http://www.maxfreak.com/diablo3/archives/diablo-3-xbox-360/
Anyone heard anything else that may be coming to the 360?