Facebook has in a lot of ways run its course. They're still iterating, but I don't really see it benefiting users much.
I don't see a sale to Apple benefiting users much either, but the fallout could be interesting. If I were him I might sell just out of curiosity to see what would happen. It sounds, if not better, at least profoundly interesting.
I don't think Zuckerberg is going to allow Facebook to be bought by anybody, he's doing the buying these days.