1. Jon Vs Daenerys
Thanks to their status as the lead characters of the saga, the attractive hero and heroine, and Jon being a Targaryen, it was inevitable that - despite the incest - Jon and Daenerys would end up together. With their focus on working together to beat back the White Walkers, it's now expected the pair will lead the living to victory over the army of the dead.
There is another theory, however, that the exact opposite is going to happen. This is based around the idea that Daenerys, rather than being the saviour of Westeros, is the real biggest threat to it. Like the Mad King before her she is going insane, and along with her remaining dragons will ruin the Seven Kingdoms.
There's not much time remaining to make this happen, but it'd be a huge shock and fit with the notion that there is one more "holy sh*t" moment left, and there is established precedant for mad Targs and late changes of alleigance.
Alternatively, it could be that Jon has to kill Dany in a more tragic way, with it being the only way to realise the prophecy of Azor Ahai and defeat the White Walkers. Either way, there's a real chance the end comes about with Jon killing Daenerys.
How do you think Game of Thrones will end? Share your thoughts and theories down in the comments.