Yep, they're ignoring the CGI Cumberbatch one, and bringing back Jim Carrey and Ron Howard. Now, the Grinch and Cat In The Cat Halloween crossover special was rancid, but Dr. Suess did write it, so it is the official sequel to Grinch and Cat. If they wanted to be really true to Suess canon, Grinch 2 would be the Jim Carrey Michael Myers crossover. Bet they don't do that though. Source. https://www.darkhorizons.com/jim-carrey-to-return-as-the-grinch/
Sincerely, what dark magic took place to make this happen? The Suess estate has flat out refused any live action adaptations after how that Cat in the Hat movie turned out. I guess the script must be a banger for them to have okayed this one.
