Um... the thread title itself is rather a spoiler, don't you think...?
Anyway, I think that the fact that physical attacks actually DO affect Blackbeard will be a big factor to his defeat. Luffy (or whoever else will fight him, but I'm about 99.9% certain that it'll be Luffy who takes him down) will have to find some way to avoid being grabbed by Teach while dishing out the damage. I'm pretty sure that Luffy will have to use the Gears in creative ways for this fight indeed...