I wouldn't because I am higher on Forte than most people. Hes gotten 50% of the workload for the Bears offense this season and been successful. IMO your only gaining value at TE with graham. I think Forte and Foster are too close to lose Calvin.
Your obviously downgrading at WR, while upgrading at TE, so it comes down to whether or not you think Foster is a big enough upgrade over Forte to take the deal, as well as how much this upgrade would cover up your downgrade at WR. Its a matter of personal preference. Honestly, it's a pretty even trade, so I don't see the point in doing it. With that said, it wouldn't be the dumbest idea in the world to take it either. Graham is putting up nice numbers (#1 TE), Nicks is still a Top 10 receiver, and Foster a top 5 RB. But is Foster an upgrade over Forte? And don't forget to consider Foster's hammy. I'd stay pat, but it is your call.