I don't think we should just dump either of these guys. Here is my logic.
If they play badly, they won't be hurting us in terms of lottery position or young player development. So why give up any kind of an assest to give away two bad players? If they play badly, just ride it out.
If they play well and heaven forbid, we actually start winning some games as a result of their good play, then they will actually have some trade value. That would be the time to trade them where we might actually get something back for them.
Humphries is only a problem for 1 year so whether he plays well or not, I am not too concerned. With Wallace, I think he can be put in a position on this Celtics team where he will accumulate some numbers and then at some point during the season, he can be traded.