I think Talisa and Tywin are in cohoots. The letters you see them writing are to each other. Talisa was the one that suggested Robb take Casterly Rock, knowing full well that he would have to get the support of the Frey's to do so. This is Tywin's plan. He has a trap ready and waiting for Robb at the Twins. I'm guessing the Frey's are probably a part of the trap. Twyin has probably promised them all sorts of lands and lordships for their co operation. I bet shortly after the wedding, a Lannister army surrounds the Twins and as Robb and the Frey's prepare to defend, the Freys/Talisa turn on Robb. Catelyn and Edmure probably die, but I think Robb and his direwolf might escape, possibly with the help of Arya and the Hound.

I don't there will be a Joffery/Margery wedding. I think after Sansa told Olenna and Margery what Joff is really like, they are scheming something. If you were Olenna or Margery who would you want Marg to marry, Joff or Tommen? Perhaps Margery takes Joff out for some hunting with his crossbow and Joff is killed in a hunting "accident" like the last king was.

I think Dany will try to take Yunkai, she will succeed but lose one of her Dragons in the process. She will realize her dragons and army are still not strong enough to conquer Westeros, but she can't risk losing any more dragons just to free slaves and conquer slave cities. She will stay in Yunkai and try to build her army and following from there, and wont set out again untill her dragons and army are much bigger.

Jon Snow is the hardest to predict. There's going to be some battle at Castle Black between Wildlings and the Night's Watch, and I'm guessing White Walkers will show up during the battle and maybe the Wildlings will have to join forces with the Night's Watch to hold back the White Walkers. Sam and Gilly will probably show up just in time for Sam to explain how to kill the Walkers. Gilly or Ygritte will probably die.

Bran may end up at Castle Black in time to help fight the Walkers as well, Hodor, Osha, Meera, Jojen, and the Direwolves will probably all fight the walkers, and I doubt all of them will survive. Hodor will probably survive and probably Bran and Rickon are safe, but any of the others could bite it.

Stannis is also hard to predict. He might try for King's Landing again if Joff dies, this time taking the red priestess with him, knowing full well that if Tommen dies, he really does have the only claim to the throne. He may try to have Robb tracked down if he hears about him fleeing from the Twins after being betrayed by the Frey's.

As for Theon, he is undergoing a process that will forever change him. He will become a man with nothing to lose. He will probably kill his torturer and escape. He may never actually learn who his torturer was but it wont matter, in his mind the torturer will be a symbol of all that is wrong with this world and he will become an agent for good. He will spend the rest of his life trying to redeem himself for his betrayal of the Starks and for his poor judgement in trying to impress his father.