Bullshit, zero sources point to that. They said it's a direct sequel, the game will have approx the same development time than previous GoW but with more workers.
They tried it before GoW 2018 but that game got canned. Let's hope this time it works.
Cory is/was working on God of War Ragnarok. I assume he will also work in the unannounced new game even if only overviewing it and providing some feedback. Who knows, maybe the mentioned Eric Williams is the one directing Ragnarok and Cory is directing the unannounced new game (which probably isn't a new IP, maybe it's a Star Wars game or Uncharted 5) and Cory is only overwiewing it and mentoring Eric.
Regarding Eric Williams, as of now he has been in the studio since the GoW 2005 as a designer, sometimes focused on combat design:
https://www.mobygames.com/developer/sheet/view/developerId,73057/
Ragnarok is a 2021 game. They won't delay it, because with Horizon they are the 2 biggest exclusives of the year. Guerrilla and Santa Monica are two of the tech horsepowers in Sony with Naughty Dog, so they must have been among the first teams to start working on PS5, which means they will have less tech issues to release their games.
They algo had a good part of Ragnarok written from when they did the original game, and there were some parts cut from there that they can use now in Ragnarok (as I remember some of the worlds). They also don't need to make all that huge work rebooting the series in terms of lore, mechanics, etc. so it's pretty likely that they may have this game faster than usual. Looking at the time they traditionally need to make a game and when release them, March 2021 would be the date. But due to Covid, add like an extra half a year. I bet they will release GoW in September-October 2021.