Not true, they have not announced if they will launch the same day as the system. Sony has only announced that they are going to launch during the launch window. That could be day one or it could be 3 months from launch day.
We will only know when they will come out when Sony makes an official launch date for the system.
I agree with Jared. Sony specifically stated they will be released in a "launch window", however that often does not mean same day. I'm sure there is a pretty good chance that at least LBP will be day 1. Companies often like to spread some of their larger releases out so it looks like they have a constant stream of good games being made.
Uncharted: Golden Abyss and ModNation Racers are launch titles and will be out on 2/15 (first edition launch date). LittleBigPlanet is a "Launch Window" title and should be out within a month of the console's launch (per an interview with Sony).