I first thought that book 5 would be too early for Dany's return to Westeros but considering the name of the next book and the fact that atleast one of the dragons now has a taste for humans, which i believe will excellerate there development, it seems more and more like it may hapen in book 5. I just thought that would be a final book kind of event but now im not that sure. Plus as gampie has mention Westors is ripe for a take over. The Starks are all but wiped out, the Tullies are alone and hurt, the Aryyns are hiding in there mountains, the Lanisters are/will be in disarea and with The Martells and Tyrell obvious allies who will stand against her?
in regards to Jon, I know there have been some referances made that would make it seem like Jon may be the son of Rhaegar and Lyanna but how many times was it stated how much Jon looks llike Ned. One of the things Catlyn was whinning about was the fact the Jon looked so much like Ned and Rob didnt. Now I could definitly come up with things that would make Rhaegar and Lyanna Jons parents, like how quickly Maester Aomon took to Jon or perhaps Ned was somehow responsable for Lyanna's death and that why he took Jon as his son or that Neds love of Lyanna and Roberts lust to kill all Targaryen blood caused Ned to take Jon and claim him as his bastard. but theres just too many referances to how much Jon looks like Ned. When I read that Jon wasnt Neds then I'll believe it!
....and Coldhands? whats up with that. At first I thought he would turn out to be Benjin Stark but since Bran saw him and didnt say anything I guess he isnt, but who is he? He seems to be a friend but.....
And what of Stannis, what will he do in the north? and does Milisandra (?spelling?) really believe he is this chosen king? Or I kinda get the feeling Stannis is just a tool and that the real chosen king is........JON!! although that would support the Rhaegar and Lyanna theory. Stannis is going to try and take the castles at the wall, Jon will kill him and then for some reason end up killing Mance and theres the blood of two kings thing.....
......and here is a prediction. Tyrion hooks up with Dany (not hook up hook up, just joins up with her).....Remeber Tyrion telling Jon how he wanted to be a Dragon

And he is a big part in getting her back to the 7 kingdoms!.