Hello all!
I've been lurking a while. I saw the finale last night.
I loved Littlefinger - I mean, hated him, but loved how compelling his character was. I hated his death, the whole 'trick' trial felt like a terrible 1980s courtroom b-movie. But with more slitting of throats. The only thing I liked about it was that he died still trying to make excuses and talk his way out of it, which was very Littlefinger, and the way Arya killed him - very quick, very in keeping with her training. The fake-out just made me shudder though.
I had hoped we'd see more of Varys and Littlefinger in the future, my favorite 'couple' from the books. Although I have a feeling we'll see Petyr's face again 
I also don't think Jon and Dany was supposed to be sexy, but more of a 'oh nooo, what are they doing?!' moment. I can't imagine Jon being ok with this when he finds out.
As for Tyrion's face - he definitely made some sort of deal with Cersei although whether it had to do with the succession is doubtful. He knows she cannot have children, after all. I think it is more likely that he has to persuade her to go back to Essos (haha, autocorrected to Essex). His job will be harder if she has a Westerosi lover. Or could she be planning on marrying her to Jaime? Could she have even planned on sending Jaime right to her, although she isn't usually that clever. Then the Lannister child would have a better claim to the throne than most, right?
In Cersei's mind, if Jaime and Dany marry, Jaime has already secured the succession, the family will be able to stay in King's landing, the dragons can be dealt with at some point by the giant crossbow, and Dany could be quietly disposed of once Cersei's child is older. From Tyrion's perspective, marrying his older brother to Dany is not objectionable - Jaime I said more or less a good guy. And everyone would be more or less happy.
Obviously it wouldn't come to fruition, but it could be what Tyrion's task was.