Looks like it will redo the original movies with new features and include Crystal Skull stages.
In the StarWars.com article there is a link to the official lucasarts LEGO IJ2 site, and there it mentions the following:
For the first time ever in a LEGO game, Build Your Own Adventure Mode allows you to create your own levels and environments and share them with your friends.
Sounds interesting, wonder how well it's going to work and just how difficult someone will be able to make their level.
Glad I bought the LEGO IJ 1 for $20, because it looks like I'll eventually get this game, too.