The Tron 2 trailer shown at Comic Con was actually a test footage to check the feasibility of the Tron sequel. But don’t worry, Jeff Bridges, seen overlooking the game grid, is indeed in the cast of TR2N. No other original actors seem to be involved though.
It has also since been confirmed that Director Joseph Kosinski has decided that the movie Tron 2 will be in 3D. Cannot expect less from TR2N!

Much more details at

TR2N In 3D And With Jeff Bridges

Great movies are lining up for 2010 and 2011: Tron 2 will still have to compete to catch the public attention.
:)