That's an interesting hypothesis. Yes, it seems possible that he released his birth certificate just shortly before Osama bin Laden was killed in order to highlight that he's a real American and a tough leader.
On the other hand, there was no guarantee that the secret mission to execute Osama would turn out successfully. If the mission had failed, releasing his birth certificate wouldn't have had any positive impact at all.
If the mission had become another Operation Eagle Claw, there was a good chance that no matter what Obama did, he would have been guaranteed being a one term President. The timing of the birth certificate release was certainly fortuitous, but since Donald Troupee was succeeding in dominating the news cycle with the birther nonsense, its release was certainly justifiable on those grounds as well. Still, it does make a good conspiracy theory. If you want to make it even better, have the Trumpster start becoming a birther mouthpiece precisely so Obama could release the birth certificate precisely when he did.