If DeAngelo does well enough this year to warrant them keeping him in 2010 with the intent of signing him for a big contract, that's just going to be that much worse for Stewart as his shot at quality playing time in Carolina will decreased even more.
So yes, I'm assuming that unless Carolina breaks trend and resigns DeAngelo to a large contract, they will likely trade him after 2009 so that they at least get something back for him instead of getting nothing by letting him walk after 2010. It is very possible that this is DeAngelo's last year as a Panther, IMO.
I think you are missing the point that Carolina likes have two gifted running backs. Carolina likes having a running back by committee. For fantasy football purposes that isn't ideal, but for the Carolina Panthers it is a very good situation. Carolina's focus is on their running game, and they are not going to jeopardize that by trading away Williams before his contract is over. They like the one two punch with Williams and Stewart. I don't know why people act like they must chose to keep one and get rid of the other. They want them both.
Yes, they like having 2 RBs. What they have yet to show is that they want to tie up a lot of money in a contract for a RB. If DeAngelo has another solid 2009 year, he's going to be VERY expensive to keep after 2010. Thus, it's very possible that they continue doing what they are doing.
Use DeAngelo while his rookie contract is relatively cheap. Before it's up, get some value back, draft another RB, and make Stewart the primary guy and the rookie the #2 punch. I'm not missing the point about what they do at all. I just don't think they will spend a fortune to keep DeAngelo AND Stewart, which is what it will cost to do so. And if they don't trade him after the 2009 year, then he will walk away and they get nothing after the 2010 year.
Options:
1. Trade him after 2009
2. Let him walk after 2010 for a compensatory pick
3. Sign him to a large contract after 2010
Which of those do YOU feel is most likely to happen given their history and knowing they have Stewart on the roster? Again, my guess is they do option #1 and draft another RB in the 1st or 2nd round in 2010 to compliment Stewart. It's what they have seemed to do for several years now.