The one positive about pumping the brakes on GOT to buy Martin time to write is that I really do think there is a ton of material they'll need to spend a lot of time building in the series, where the books kind of go through it quickly and work better on re-reads...
I think fans honestly underestimate how much time it could take to build out some of the arcs that start to build across AFFC, ADWD, etc for a TV audience.
(SPOILERS BELOW, sorry not just how to tag)
1. Pretty much everything with the Greyjoys and the Kingsmoot.
2. The Golden Company, Aegon, Griff, and the thousand things I don't even remember about the Blackfyres, all that stuff.
3. All of the Dany Mereen/Sons of the Harpy/names I could never remember drama.
4. Stoneheart, if they go anywhere with that. Hard to say right now.
5. Pretty much anything with Ramsay and the Night's Watch, fake Arya, Theon's redemption arc. And Frey pies of course.
6. Real Arya and Braavos.
7. The Sand Snakes...
8. Reintroduction of Myrcella, Darkstar, etc.