I don't think you can categorize it by just years on the market, and if you are then you have to look at what's most recent, which is last generation. Sony released the Pro, Slim, and the PlayStation VR late last year, so releasing another major console next year wouldn't make any sense, as you're throwing away a lot of potential money and developer investment to the wayside. Maybe in terms of timeline, it is smarter to look at the distance between when Sony released the PS3 Slim vs. when the PS4 came out, which came out in 2009. So if you want to look at timelines, we're potentially 3-4 years out from another PlayStation console. Iterative hardware like the slim and pro is not new.
The PS4 is selling at an astronomical rate, so it would be absolutely ridiculous to assume that Sony would just drop a majority of those sales in order to just put out a new console, when the full potential of the PS4, sales and performance wise, have not yet been reached. Why would Sony put out a new console when there's still dozens of exclusives still to come within the next 1-3 years for PS4? Why would they release a new console, which they would lose money on, when they are making a profit off of the current hardware that is not showing signs of slowing down in the sales department?
I realize it's just a rumor, yet I've yet to see it pop up on any of the sites or here from any of my sources that I typically deem credible. It's fun to debate rumors and speculation, but this one is far too unrealistic for my taste. We'll see the PS5 no earlier than 2019 or probably 2020. There's just no logical reason for Sony to release it before then.
Don't get me wrong, I'm not trying to throw shade your way, I think it's an interesting discussion. I just don't see how or why it would be feasible seeing how Sony is set up currently.
