Well I guess first of all we would need two big ships, one for the imperials and one for the pirates. We got Eldorado Fortress so we would need some kind of Hideout probably a little island so the Pirates don´t need to stay on water all the time ;).
The two Ships would obviously be the top of the price list and the outpost wouldn´t be in the range 80-100€ I think, so only lower price Sets are left for the rest. I think there should be some little 10-15€ Sets. Little fun Sets with things like a row boat, a cannon, treasure chests etc and two minifigures, maybe a skeleton. And for the mid-price Sets there could be a Bar on the beach with a little dock, where the Pirates can drink some rum ;).
Well there are some space Sets, but they are all in different themes. City, Friends. CMF (that is actually the one I am most curious about). And then we got the rumours about the Lego Moments. So if the first infos are true, this could indeed be a new theme picking up on old Lego Themes and Sets - but sadly looks more like two sets a year or something (one in April, the other one on the spot of Lion Castle, Eldorado Fortress and the Classic Space Ship). However if that wents well they might still increase it in the future.