Well, I think they're focussing on their new shiny thing – raytracing – and perhaps not wanting us to figure out that we won't be raytracing at the framerates and resolutions we've grown used to. No-one's going to be playing Shadow of the Tomb Raider in 4K at full settings plus raytracing at a playable frame rate this generation, that's for sure, that's still a generation or two out. (Same as 4K/60FPS was a few years ago, which has only just changed with these cards.)
But in terms of the games we'll actually be playing, without raytracing, there's no reason to believe that this isn't just another generational bump – we've had a 20-30% increase in performance each generation for quite some time now, and given it's been 18 months since the 10xx series was released, I'd be surprised if we didn't see that or slightly better in most situations.
But really, it's impossible to draw any conclusions until after the cards launch and reliable reviewers get their hands on retail cards with production drivers. Until then, it's all wild speculation and, I suspect, more than a little fear-mongering.