This is one key point that I think Marvel and the fans recognize, and I think this could be the biggest reason Marvel may open their check-book and do what needs to be done.
When we got a glimpse of Thanos in the Avengers, I couldn't help feeling that it was a bit of 'kissing your sister' moment.
Sure it was cool to see him, but without Galactus out there somewhere, Thanos isn't Thanos and the Marvel Universe isn't the Marvel Universe.
I'm an FF fan first and foremost, but even from that perspective, I recognize that the Marvel Universe can exist without the FF, but it can't exist without Galactus.