That's the plan. It's too big a book and has too much going on to fit into a 10 episode season. HBO seem to fixed on 10 episodes per season, so the best option was to film it over 2 seasons. It'll be rather tricky to write, especially since some stuff from book 3 was brought forward to be in the 2nd season (mostly Jaime and Brienne). The harder ask will be trying to combine Feast and Dance if they get that far.
