I do not think FB will pull anything like that. Even if tey do, I'm pretty sure Opera is ruined. They took Snaptu some time back and ruined it.
I had been using it for quite some time but Facebook came, closed everything except FB app in Snaptu and moved on.
I just hope they do not get Opera.
Money is powerful and everything, especially if you don't have it, but I think Opera knows it best it will lose a significant part of its core usergroup if this goes through. They would essentially ruin what they fought for all these years