Last I heard, the widespread internet favorite was TRON 2: Electric Boogaloo.
But seriously, when are they just going to pick a name and stick with it FFS. TRON 2 or TRON 2.0 would be the best titles, in my opinion. Followed by TR2N.
Even though TRON 2.0 might confuse some people, simply calling it TRON will confuse them even more. And TRZ? Just idiotic.
At one point they were thinking about calling it TRON 3.0, but that was a long time ago.
If it wasn't for the fact that all the recent articles out there, and even Jeff Bridges himself, are referring to it as a "sequel" . . . I would be worried that this signaled the film was actually a remake. *Shudders*.