No idea if UBI will actually make a From Dust Sequel or DLC content for it but an Idea that has been floating around in my head seems like a possibly awesome addition!
it would not actually involve more then one player on any map at a time, but sort of "map sharing"!!! at the end of from dust you are put into the empty ocean with no villages and only a spit of land to start up your own custom island! what if UBI were to add a simple scripting into it! to make timed events happen, and other challenges, make this system easy enough for anyone to use but also so that when a map is done, that map can be shared and DL'ed in a central location (like the Elder Scrolls workshop in steam) these maps could be downloaded and played by other people! and if the simple scripting of events was enabled, those same maps could become challenge maps!
Add in the functionality of map transitions when a given map is finished, and players (modders) could string maps together to make their own journey for the natives! the event scripting could be as easy or easier then the scripting system in making maps for Stronghold 2 and all done in-game! it would definitely give a game like this more staying power, and appeal to people! I know UBI has a lot of creative people, but think of the insane creations from the general gamer collective!