LinkedIn profile of one of the Rockstar Games employee claims that Red Dead Redemption 3 is in development. This is the page of Lead AI and Gameplay Programmer from Edinburgh office.
Through 7 years he worked on gameplay, AI, physics, and other systems for Rockstar titles.
Recently Take-Two CEO confirmed that the publisher will work on expanding GTA and RDR franchises, so there is a change that is a legit screenshot from LinkedIn and RDR 3 is in development. On the other hand this is could be just a simple typo. Please take this as a rumor until official news.