This leak is so obviously fake it hurts.

Why do people pretend (LARP) that these leaks are real?

I think it'd be more fun to do a "What if?" and a "Wish list." Basically, saying what you wish the PS5 will have and what games will be on it, rather than pretending to be a leaker.

Game contracts late in the gen. I don't think so. They are gearing up for the next hence they are visiting MS already. 

Also, a lot of people here are talking about sales and such for the PS4 but ignores that Sony cannot afford to give the new Xbox a 1 year head start again. 
Currently Xbone is not doing so hot and MS wants to start the new gen badly. As I said above they are just waiting for the next box and they will follow suit. They have the leverage of a waiting game  because of PS4 while MS needs to be aggressive at the start. 

The initial development kit rumor may be true, but the following leak is complete BS. Early 2019? No. The earliest we'll see the PS5 is late 2019, with an announcement in early 2019. Two varients at launch? Nope. Sony prefers an easy launch for consumers. They aren't going to change that and release a $499-$599 Pro with the normal PS5. They'll follow the PS4 Pro model and launch it mid-gen, when they can get more power for less money. Leaving AMD for expensive custom HW? Lol, no. I'm pretty sure Sony already said earlier this gen they are staying away from custom HW. And B/C with everything, BUT PS4? And because they feel pressure from MS, who at best will sell half of what the PS4 will? Bwahaha. No. If there is any B/C, which I think there will be, it'll be firstly for the PS4. The others will be icing on the cake if they do support them.

Q1 2019? Bullshit is off the charts on that one.

Not gonna happen so soon. Also, backwards compatibility with PS3 sounds a bit suspicious.

In 16' we got ps4pro, guessing this yr pro slim premium w/4k player ($399), so maybe '20 will be the earliest for PS5.

I don't understand why ppl think Sony will release a new console this fast while PS4 is still growing in sales every year, why shorten the life of something as sucessfull as the PS4 ?

If MS release their box devs would just make games that could run on PS4 and MS new box cause they aren't about to ignore a 75M install base just to have better graphics in their games, so Sony can wait and release something more powerfull and cheaper than MS like 1 year or so after MS releases their box.

This leak is false, obviously. But even if dev kits were out there, it wouldn't necessarily mean 2019 release. Could be 2020.

Sony obviously don't want to repeat the mistakes of the PS3 launch i.e. launching late, at too high a price point with unique hardware architecture. They want to follow the PS4 forumula and get the one-up on Microsoft. I can't see them launching earlier than lat 2019. The first rumours of the PS4 Orbis dev kits were in early 2012 I think, so that would match the time frame. Red Dead Redemption 2 and The Last of Us 2 as launch title would be killer. BC is a must this time too. There is always that 12-18 month post launch peroid that generations share the same games.