GTA 4 is coming out on April 1st, 2008.

I preordered GTA 4 for my PS3 last July, and last week they sent me an email telling me that the release date for GTA 4 was changed to April 1st. Before the date had been changed, the release date was sometime in March.

I'm not sure about Rainbox Six Vegas 2

Edit: I found some info about the release date on Rainbox Six Vegas 2. It is scheduled to be released on March 11, 2008 and is coming out on the 360, PS3, and PC (Windows).