According to this article from NFL.com, Bucs RB Carnell (I refuse to call him Cadillac) Williams is on pace to return at some point during the 2008 season.
As much as I might cheer for the guy to get better after a major knee injury - you never want to see anybody hurt - I think that the Bucs might actually be a better team without him.
The young Mr. Williams has an annoying tendency to go for the long, highlight-reel run rather than simply taking what the defense gives him. This tendency results in occasional long runs, but it more often results in runs that gain little if any yardage and leave the Bucs trying to convert the kind of second- and third-and-long situations for which their offense is ill-equipped.
Earnest Graham is actually a better fit for the team's offense right now than is Williams. Graham isn't anywhere near as talented as is Williams, but he runs straight forward with power and gets positive yardage, leaving the team with manageable situations.
If the Bucs can get a reasonable offer (a second-round pick or a starting-quality CB or DT), I'd favor them trading Williams away. He's been a member of the team for a long time now, but he's just not a good fit at this point.