Lets get a timeline going for rumors, speculation, so called leaks, and conjecture. If im missing something please remind me. I probably have some sequence of events out of order.
-Summer of 2017 an insider on this very forum "Matt" claims PS5 "Will be a half step and release 2019."
-Some months before E3 2018 we get articles about how sony and AMD have partnered for Navi GPU.
-E3 2018, Microsoft out of the blue starts talking about next gen and claims they will Be the benchmark to beat, or something to that effect.
- Late December 2018/January 2019 so called insiders claim ps5 devkits have gone out.
Also around this time a linked in profile from Square enix mentions a PS5 title as well.
-Early 2019: Non stop, almost daily articles from forbes and windows central about "Microsft dominating next gen" articles.
-We get information from MS Propaganda pieces Brad Sams and klobrille that Xbox is planning a 2 pronged approach. A lower end weaker model called lockheart and more powerful one called Anaconda.
-Shortly after that, Reports that Navi has been delayed for some reason.
-April, The Mark Cerny Wired Interview. Vague details are given about ps5. It sounds alot better than i think most were expecting and relays fears about backwards compatibility, at least with ps4. MS so called insiders went on pure damage control mission claiming Anaconda will certainty be more powerful. It was also after this interview that all the articles about Xbox dominating next gen stopped coming out. "Wait for E3" Was the new Mantra.
-Albert Penello, former xbox suit expects ps5 will be around 8 terraflops in the next gen thread on Pedo era.
E3: 2019- Xbox Scarlett is briefly mentioned. More a retread of the ps5 wired artcle than a proper unveiling. No mention of lockheart and is somewhat implied to be a single console.
-Xbox scarlett architect leaves microsft for intel. Rumors start to trickle out that PS5 is more powerful according to devs. Rumors are currently swirling that lockheart may be cancelled.
My interpretation of it all: I believe sony did intend on launching in late 2019. Navi getting delayed messed up their plans but the technology was probably very much improved. Xbox, certian that sony would launch 2019 with an 8 terraflop console devised the 2 prong approach a rumored 4 terraflop lockheart, and a more expensive 10-12 terraflop anaconda.
Sony being a hardware first company and being involved with navis development made a better or more efficient chip than xbox did for anaconda. All the meanwhile dev kits for both systems start to come out and developers beging to compare. MS slowly walks back the lockheart because there would be no point to having 2 weaker console. I also belive they got feed back from developers not wanting to be contained to 4 terraflop hardware. There were also rumors that lockheart would be disc less as well. They probably got push back from retailers and threatened to mark up the deceive or in gamestops case not even carry it. All of this is my speculation of course.