I'd like to pitch a "double finale".
Let's jump to it.
Assuming the show continues successfully then I'd imagine they'd wrap it up in a similar tone as the rest of the series. Light hearted, fun, a nice little send off to the story would work great.
But we know Dunk and Egg's tale doesn't end there. Their story leads to Summerhall and don't we want to see that? Dunk and Egg in the future, the extended Targ family being there, plus seeing an event that GRRM still hasn't given us the true details for.
I'm suggesting they finish the proper main story and make the series finale end in a true dark and disturbing Game of Thrones way.
A tv example of this would be Justlice League Unlimited. S4 (or 2 of Unlimited) ends led with the heroes saving the world and all..and the finale jumps into the far future and concludes the Batman (Beyond) storyline. Both episodes were amazing and I love that it ended in a completely unique way. So copy that!
Basically I want to see Summerhall play out and this would be the ideal moment and time to make it a reality.