See, but PCs aren't relevant to the discussion; that's a whole separate argument. I'm a PC gamer primarily and PCs are a whole different beast. You fiddle with everything, you likely build a more expensive machine (yes, I know $400 "console killer" PCs exist, but frankly you're more likely to splurge on parts). People don't necessarily want that.
So they look to the alternative. Hey, here's this static thing for $400. If history is any indication, it stays the same for 5-8 years. It offers fantastic return on investment, and is at the forefront of every developer's mind for those 5-8 years. It gets the first class treatment the whole way.
Now it doesn't. Now I'm sure a lot of people (especially those who purchased in the last year or so) are wondering why they didn't build a PC.
And of course there are no rumblings in store. There's no marketing yet. By and large, the public probably doesn't even know a "PS4k" is in the pipeline.
Return on investment? You are able to sell the PS4 for more than you purchased it? And no it does not get 'first class' treatment the whole way because, especially with this gen, it was never first class technology to begin with. It was simply an affordable compromise and it remains that.
On a side note, if the PS5 does come in 2018/19, I really, really hope they skip Vega and jump straight to Navi. With that being said, PC gaming is looking more inciting to me than ever before.
Remember that the PS4 is a semi-custom GCN design so they're not strictly bound to stick precisely to AMD's architectures. Either way Playstation's will likely continue to use chips which make 'economic sense' as opposed to chasing out and put power going forward.