GW is still getting grief for getting rid of the Squats in 3rd edition. Making major changes to their flagship army? Probably not in this reality.
Besides, as others have said, 40k (and for that matter, WFB), is a setting, not a timeline. GW exists to sell toys, making sudden massive changes in the setting is not going to help them sell plastic. In fact, it would probably hurt their sales, as well as piss off a whole lot of people. I just can't see GW doing something that silly.