I've said it before, and I'll say it again, just make sure you sell them before he dies. Villain books never hold up their movie hype once the villain is done.
I would agree. How many movies are they going to extend the Thanos battle into -- you really cannot justify 1 film battle. I would say how about the first battle being a complete slaughter for the first film with a group of heroes in critical condition. Then the second film bringing in all heroes from all groups to battle with a barely win situation.
Seriously though -- How many film studios and production companies have teamed up for financial benefit to keep costs down and then share the profits on huge budgeted films?
I believe a giant cross-over/team-up is capable for X-Men, FF and Spider-man to join in a battle with Thanos as well as the Civil War.
But it's a great key book in general.