Yes, you will eventually return back to your family but you will be older and such. As for your quests, I can't really remember too well on that but I think you should still be able to do them. In case your quests are gone, you should totally do them before you start the "Spire" to ease your mind on losing them.
Well, I don't play Mw3 too much and I'm nowhere near 10th prestige. I do however think that they are trying to satisfy a lot of the people who are maxed out at 10th prestige able to get some progression. In my opinion, I think the new prestige emblems are just lame/lazy. A lot like the rest of the game. :)