So by the end of Prometheus, we know that Infected Host + Impregnating Another (via good old intercourse) = the creation of a facehugger (or indeed 'body' hugger) and Body hugger + Host = Xeno. Or close enough. Also this Xeno's placenta seems to hold a heartbeat which Ridley seemed keen to highlight, so potentially Xeno with a bonus facehugger egg to boot. I suppose one route for future sequels is Weyland's company arriving on LV-223 to find out WTF went down and discovering baby Xeno, capturing it, sending details back to Earth and them loosing it (someone probably blows it out of an airlock or something). This would explain the Nostromos re-routing at any signs of alien life and give Weyland Industries a connection to know what they were looking for. Either Engineer or Xeno based.
The other possibility, and no doubt the one Ridley will take with sequels is Shaw and David's head fly off to the stars and find The Engineer's home planet where we gain a deeper understanding of the "military base" on LV-223 and their manipulation of life in the universe. As hinted before this sounds like a trilogy, with the final instalment being the one that connects Prometheus to Alien. As a quick guess. Shaw befriends the Engineers in Prometheus 2, Avatar style and in Prometheus 3 she leads them back to LV-223 to discover the Weyland follow up ship taken out by this new species of Xeno. The Engineers and Shaw nuke the whole planet from orbit but with one Xeno inside the last Engineer, the chest burst wipes out a race, crashes a ship on LV-426 and the eggs, xenos and fossilised Engineer sit alone in silence until Ripley and Co. turn up to investigate the crashed derilict ship years later.
So guys, over to you. Thoughts on the back story (because these are just ideas remember) and of course what you think the future of this potential new franchise might be. Will Ridley direct them all? Do we need new writers for the sequels? Will James Cameron do Prometheus-s?