Well, with the upgraded versions of the PS4 and the XBone coming next year, it seems the console market is going to follow less of a traditional generation and more of a 2-3 year upgrade, at least if those are successful. If the PS4K and the XBone.2 are indeed a success, when are we going to see the next upgrade?

I think its kinda simple. There is a direct relationship between the possibility of such revisions to the available manufacturing technology.

Imagine that fir a sub $400 console to exist, it will be limited by its power draw which directly relates to how much heat it puts out. At any given manufacturing process, there is only so much you can do if you are trying to make a sub $500 box.

The best they could do at the price they were targeting in 2013 was what a 28nm process would allow. Now with a 14/16nm process they can do much more and still fall into the same price bracket and thats what we are seeing now.

Short answer? We will see successors when chip foundries have a 7/10nm process. On the current process, GPU makers can only put more and more and more cores on a chip or find other ways to improve performance be it memory or frequency or power. Consoles don't have that luxury.

Mind, this has always kinda happened before. The PS3 went from a 90nm process through 65nm all the way down to i think 28nm now. There were basically at least 3 chip revisions Albeit the emphasis then was just going smaller and cheaper. It also didn't help how exotic those chips were so a lot of R&D would have been spent if they tried to go smaller and more powerful at the same time. But now, the focus is different. Rather than go smaller, they are going for more power. 

Probably three years later.

I think that these console will be upgradbale for many years, but if there not then maybe around 2021-2022.

I stay with a release in 2017 and the PS5/Xone launching in 2020

2017 - PS4 "Pro"
2020 - PS5
2023 - PS5 "Pro"
2026 - PS6

Can people not count?

PS4 & XBO released in 2013.

PS4 Neo & XB Scorpio are rumored to released in 2016 & 2017.

That is not 2-3 years, that is 3-4 years.

I hope this is a once only sort of deal.
Or if it continues this way that they lenghten it to every 4 years or so instead.

I expect Playstation 5 in 2020.

three years is the only valid option
as an early release. 4 is possible, too
just not 2 or less

I see this as something that will hapoen every 3-4yrs. Right now it just makes too much sense. Switvhing to X86 hss the benefit of having reduced the billions they woukd typicwlly have invested into R&D to make their own exotiv chips. Now someone else does that for them and they just modofy it a little. 

And there is also the fact that this allows them retain their entore user base across generations or versions. If by 2021 the PS5(PS4.9) is released and there are already 100M playstaion owners or 80M Playdtation gamers with PSN accoints and years of content tied to those accounts; they arent going anywhere as lomg as PS5 games can also be played on their consoles. Its an ingenious way to circumvent the singke biggest problem consoles present.