The whole point of SemiAccurate is to report "true rumors" before they become official, so pretty much everything they publish is officially denied. So either this article is completely wrong or it's right but AMD isn't willing to admit it yet.
I don't know, but considering the transition would happen within 2 years, I can see how they wouldn't want people to find out 2 years earlier about it.
Of course they're going to deny it. Even if completely accurate, it's going to be a staged transition and they'll try and salvage as much as they can from current Steamroller R&D. I guarantee that AMD will do at least one more high end CPU. Without the high cost of R&D charged against them, AMD can much more easily make money on its chips, and it will do so as long as it can.
The chip might look more like Piledriver than expected, but it will have some Steamroller bits and will probably be called Steamroller.