I haven't read anything on predynastic use of oases, but that's an interesting point. I'd guess that nomads from Arabia who had been living on oases there may have migrated into Egypt as well in predynastic times.
There's an old theory in predynastic Egyptology that the prehistoric Aterian peoples (basically desert dwellers) were forced into the Nile Valley by the climate warm-up and that this helped push population densities up and encouraged more agriculture. I think it kind of got blown away when it turned out this happened in the 30,000-40,000 bp range, rather than more recently.
Still I can't help but picture Al Gore going from hunting camp to camp in his loincloth - "the climate is changing - we're doomed!" - just before said climate change kickstarts civilization. :)