I think they should wait for a better deal. His stock is not necessarily plummetting as a result of his play as any general manager knows that a disgruntled player isn't going to perform as well as he normally would.
As the season rolls on there are going to be some teams not meeting their expectations who will be more willing than now to give a better offer. They'll be somewhat more desparate. In the meantime the fans here see that the offers aren't good enough and due to the tormoil, they can't very well expect the team to challenge, so some of the pressure to achieve is gone.
As well, with Vince seeing the low quality of trades his value is bringing in, it might spur him to play better in the hopes the Raptors can get enough to satisfy them and expedite his departure.
The only big danger I see in waiting longer is ..............INJURY. We all know how fragile this guy is and if he gets a significant injury, they're fucked. Otherwise waiting is definitely the smart play.