Yeah I think the story line will be somewhere along the lines of this. The UED hearing about defeat sends more ships to save Earth, The zerg now under kerrigans power will just sit on Char or the few planets they control and build up. The rest of the terran will probably run and try to rebuild and come up with some amazing new technology. All the while the Protoss will be finding there way and working with the dark/light protoss to become a huge race that can survive... Then the Xel-Naga will show there face, Mad at everyone and everything that destroyed there brothers and sisters that created the zerg and protoss. So of course all the races will have to deal with the hatred between themselves and try and fend off the Xel-Naga. At the end there will be no victor, just massive losses on all sides and all that are left will run, hide and survive. Sorry if this dont make much since, i was in a hurry writing this!