From the trailers it looks like there is a VERY strong chance that the two remaining MIA Starks – Bran and Arya – will finally return home to Winterfell, and honestly we're already a little moist-eyed at the very idea.
The problem is, as Isaac Newton nearly said, "Every action has an equal and opposite reaction that rips your heart out through your eyes until you can no longer understand the concept of hope." In other words, good things don't go unpunished.
Death-proof Jon is wearing Valyrian steel plot armour and Bran needs to continue his role as Lord of Exposition, so if they want to break us with some long-overdue Stark-killing (Rickon doesn't count; it was his own stupid fault for running in a straight line) then we're left with Sansa or Arya. My money's on the assassin, rather than the one who will probably stay inside Winterfell for the entire season.
Likelihood: 3/10 ???
How: Honestly I think perhaps this season is a little too soon for Arya's demise, but if it were to happen...being killed by an ally when masquerading as someone else would be suitably devastating.
2. Littlefinger
Ever since he convinced Lysa to murder Jon Arryn, shit has been going down in Westeros. Wars have raged, kings have come and gone, the continent has been torn apart, and it's pretty much all Littlefinger's fault. What a dick.
How he's escaped retribution up to now is anyone's guess – however, Bran's return to Winterfell could just be the turning point. Ned Stark's only remaining son has access to, seemingly, all information ever thanks to the World Weirwood Web. As soon as the remaining Starks work out that their parents and brothers would still be alive if it wasn't for Petyr, surely it won't be long before Arya adds him to her list.
Valar Morghulis.
Likelihood: 7/10 ???????
How: Arya opens his throat – Frey-style – with Baelish's own Valyrian steel dagger, which caused so much trouble way back in Season 1 after he told Catelyn it was Tyrion's.