Even if KC is out of contention, Gonzo is going to play. He's had that injury for a long time now. He should have had the thing taken care of last year. I don't think he's going to stop just because he's going to get surgery in the offseason. He's going to play and give him team a chance to win even if they are out of it. If it gets hurt worse, he's just get it done sooner.
Gonzalez is starting to pick up the production again, so I'd probably ride it out. At this point, there aren't a whole lot of useful TE's out there you could use to supplant him. So, unless your trade for him involved a TE, it wouldn't help you to get rid of him...you'd only be lessening your chances to score.