You've got this topic for suggestions and ideas like that: http://www.gamesas.com/topic/1364939-fallout-4-speculation-suggestions-and-ideas-thread-59/
And no, not really. The Enclave are pretty much dead except for a few dozens maybe, the Brotherhood is really only prosperous in D.C. and maybe around Chicago, but back home in California they are dead and pretty small in Nevada. The NCR and Legion conflict would be rather unoriginal to have again, especially since if there is no Enclave or Brotherhood left in their general area (the southern half of USA), why by the way are also an unoriginal idea to have in a conflict again. The same goes for a "major group of super mutants". They were wiped out in California, and the remnants scattered as they fled east, slowly dying out. Then they show up en masse in a vault on the other side of the country, and yet again they are wiped out (most likely, since they have run out of FEV and you told Lyons about their source.)