The creators of Assassin's Creed 2 said it before. By performing certain missions of the game, Ezio will be able to get the support of armed factions ready to help him at any time. Here's the proof by image, even if it's not the first time we see Ezio's friends lending him a hand. Thank's to MitchBuchannon from the forum for his sharp eye.
@Tiz: John finds out he's Dany's nephew after countless banging sessions. He finds out who his family is, but has sex with his aunt. I'd say that's a bittersweet way to end things (1 Hour ago)
@KORNdog: I'm hearing the word 'bittersweet' being used a lot in conjunction with the ending. Could be a union of all the Kingdoms facing the long night with casualties in the millions. (10 Hours ago)