I doubt that anything will actually happen, but the possibility that Halladay will be traded is a good thing for the Tigers because:
1. If traded, he almost certainly won't go to any AL East teams, ruling out the potential for the Yankees or Red Sox picking him up.
2. If traded, it is highly unlikely he will go to another AL Central team, as only Chicago can afford to take on his salary and their pitching situation is fairly good, so they probably won't be willing to meet whatever Toronto's asking price is.
3. The Tigers are the other team in the Central that can afford him salary wise. Unfortunately, it is almost certain that the Tigers will not be able to offer anything that Toronto will accept. That said, should Dave Dombrowski decide that he really wants Halladay, he is one of the few GMs in the Majors who has the balls to be willing to trade away good players and prospects to get him.
4. Halladay is not likely to stay with Toronto when he becomes a free agent in 2010. If he is traded, it will probably involve a team that we wouldn't mind him playing for (Yankees, Red Sox, other Central teams). He may be willing to sign an extension with this potential new club, which would keep him in a position where he does minimal damage to the Tigers.