If we being real, there probably wont be a RDR3 anymore. The visionary mastermind braintrust of R* executives that really made this game tick and poured their souls into the unique SP experience have all left the company.
Take 2 let it be known that it now only prioritizes Online modes from here on out. So expect them to try and milk Red Dead Online for the next 10 years or as long as they possibly can just like how they did with GTA.
The next title will likely be a re-make/remaster of RDR1 which would still be pretty cool atleast