Techland are a busy bunch, aren't they? While they're not working on Dead Island's first sequel proper, they are working on the similarly themed (and quite grand looking) Dying Light, as well as producing the digital-only hack and slash fantasy game Hellraid. It originally started out as a mode for Dead Island (thanks Wikipedia!) but now is its own standalone game for Xbox One, PS4 and PC.
Beyond that I'll admit to being largely clueless, so Ian Higton's primer and interview with producer Marcin Kruczkiewicz came in quite handy. Oh, here it is right now!