What you guys think 'bout Jorah and his infection? I guess there will be an ambush of the Sons of the Harpy in the arena (if i remember correctly there was such a scene in the trailer?) and he will give his life to save Daenerys and finally redeem himself...and touches her while doing it, boom Grayscale.
On the other hand...he might win the arena fights, as the winner he earns the opportunity to face Daenerys (Gladiator anyone?). Once again she outcasts him, this finally crushes his hopes an he's out for vengeance - and touches her, boom Grayscale.
Cure? Shireen is the proof it can be stopped, Stannis knows the healer...in exchange, he needs her army and dragons to defend the kingdom.
Or maybe he infects the whole population or at least Daenerys troops, might finally drive her crazy and cross the sea to bring some dragon love over the kingdom.
Of cource it won't go down that route, just a little mindgame
And how 'bout Ramsay? Stannis troops are already in a bad shape...maybe he manages to do some serious damage to Stannis, some kind of ambush or a ruse to get the Wildlings and Stannis' troops to fight each other. And Stannis, i a desperate act, finally obeys Mellisandre's king's blood sacrifical plans.