I dont know about all that.
If
1) Vega releases earlier in 2017 than June/July
2) Nvidia does not have Volta ready to go that year as some have rumored(which goes against Nvidia's own roadmap)
and
3) Vega actually does deliver on the promises that Polaris was to have in terms of efficiency
I think AMD could definitely still be quite relevant.
However, if any of these things dont come true, they are going to have a hard time. At the very least, we do know that Vega is an enthusiast-targeted GPU lineup, so they will at the very least be providing *some* kind of high end offerings. And I wouldn't be so quick to write them off this early. They'll have the added benefit of more development time and likely improved yields from 14nm chips, so even if it's not a Titan X-destroyer, could still provide an entirely competitive and attractive product.
Of course they would. Just because your product isn't good doesn't mean you dont still try and sell it.
I'm not saying Zen wont be good, but them advertising it is a necessity, not some sign of major confidence. They have a lot riding on Zen and cant just be silent about it.