We'll see ! I don't except that much difference price/performance ratio against the 470/480, but let's wait for the numbers
I can tell you for a fact that AMD has their own crypto currency hardware lab that tests mining using their technology. It's a multiple $100 million+ market that is growing at break neck speed. They would have to be idiots not to care.
Sorry to be a skeptic, but.... Source?
These days, you never know. It may be an actual fact, or it may be a Trump'ed fact (i.e. propaganda fiction).
I don't know about marketing to miners but mininig programs are good for perforrmance and stress testing.