The way this rumor started making it all plausible. It started at Sony's VR event where a lot of developers openly (but anonymously) talked to Kotaku about how Sony is making a new hardware to take advantage of VR. That dialogue changed from VR talk to PS4.5 talk, to PS4K talk. Eurogamer verified it independently. Wall street journal also independently verified it.
Then we have a lot of folks here who are in touch with developers, as friends or colleagues, and folks that are developers themselves. Whenever someone at GAF claims "I KNOW A SECRET! THE ANSWER IS BLUE!", Mods will generally contact the person making such claims and ask for the proof or credentials. Any false proof or credentials results in either a ban and/or discrediting the user's inside secrets and connections.
OsirisBlack is one of the few verified folks who know the right people willing to talk. In return, those folks get anonymity and folks like OsirisBlack can have a conversation with them about major rumors and dispel it or shine some further light at it. It's safe to say that this rumor is 95% true, with 5% hanging on the shoulders of Sony or Microsoft themselves on what the final specs and price and release window may be. It's predominant that the push for better games and better hardware and better experiences and more options is becoming a priority. Plus, there's always a race on who adapts the newer technology first. VR and 4K and open-platforms and cross-platforming is the buzz of 2016, and all these things require a more powerful hardware that is not outdated when it releases. Hardware is rapidly changing every year and it's not only the desire to stay relevant with the exponentially advancing tech market but also, in a way, of keeping the business afloat. It helps chip manufacturers and game manufacturers to think outside the box and not be constraint by the device their idea is about to be flourished in.