FFPeasant a terrible source of information. Feelings are not facts. Also he doesn't work in a production setting, so the likely-hood of him being correct on any of his statements is doubtful. It is more than likely that FFVII will be on both PS4 and PS5 considering its a multi installment and the first chapter of VII will be out by the end of 2019 (wishful thinking) to late 2020.
Pez only really reports on things he finds via forums or article postings, so he's really only as good as his sources. But I don't think he's wrong necessarily, they very well could say "Nah... Y'all gotta buy this PS5 shit now, son..." and everyone's going to buy it while making rant videos and articles about Square Enix has screwed them over
yet again. People want to complain, but I'm not sure what they're expecting, did they want another XV? Because a lot of people (not me) complain about it not being finished. Did they announce it too early? Yeah, but even they acknowledged that. And that's why I don't mind waiting, I'd rather they knock it out the park and have them fully confident in what they're doing, rather than letting a bunch of fans on the internet stress them the fuck out and they ship out a game they're not proud of and have to do an apology tour about letting fans down and doing DLCs to make up for it.
2019 seems fair, I'm thinking 2020 though. KH3 is a definite 2018 title, and that probably isn't dropping until later in the year. If they were to release KH3 in September, best case scenario could be to release the FF7 Part 1 Demo around late-October/Early-November, just to throw a bone out there. 2019 I would think is FF7's year, since I don't think they'd have any major IPs that would conflict, unless I'm forgetting something.