3/4/5th ed where all along the same lines just minor changes.
Hahaha yep like Tuatara said, people have threatened to simply use these rules instead if they turn out to be fake.
That Dakkadakka thread turned up a few interesting things, like how it seems to push owning bastions etc. as stratagem peices, sounds like vehicle dice may make a return, and if they change the core enough, current armies will likely need new models to adjust, all leads to more sales which sounds very GW.
There is a second thread that goes into the idea's behind this being part of GW's long term 40K plan, working on this solid rule set that they use for the next 8+ years while they work on expansion material and new models with rules based in White Dwarf books, this cuts down on dev and testing time constantly updating core rules and army books and lets them make more models which is where they actually make the profit.
Thread found here;
http://www.dakkadakka.com/dakkaforum/posts/list/423481.page