Definitely, 3.xe being published under the OGL has had some positive effects for Wotc, as it has also had some negative effects for Wotc.
It is not that the OGL can be only good or only bad.
Now, one has to weight how much positive, how much negative that was, balance them out and make an informed decision whether the net effect of the OGL is a positive or negative one.
Personally, I believe that the negative effects outweight the positive ones, judging by what we have seen regarding Pathfinder and the OSR. Also, contrary to what some have suggested, even if 4e were OGL, I doubt that we would not have seen something like Pathfinder or that 4e would have been more successful in the long term. The primary reason for success or failure is the game itself, regarding the expectations of its fans. If it is what fans want it to be, the game will succeed. If it is not, then not so much.
It is not that the OGL can be only good or only bad.
Now, one has to weight how much positive, how much negative that was, balance them out and make an informed decision whether the net effect of the OGL is a positive or negative one.
Personally, I believe that the negative effects outweight the positive ones, judging by what we have seen regarding Pathfinder and the OSR. Also, contrary to what some have suggested, even if 4e were OGL, I doubt that we would not have seen something like Pathfinder or that 4e would have been more successful in the long term. The primary reason for success or failure is the game itself, regarding the expectations of its fans. If it is what fans want it to be, the game will succeed. If it is not, then not so much.