https://wccftech.com/rockstar-is-100-focused-on-red-dead-online-rather-than-any-rdr2-single-player-dlc/

Rockstar is not working on any Red Dead Redemption 2 single player DLC, in case you were hoping the opposite (despite the lack of any single player DLC for GTA V). Katie Pica, Lead Online Production Associate at Rockstar, confirmed this to VG247.

We’re 100% focused on online right now, because like I said, there’s just so much to do, and we’re just hoping to bring everything that a player can love about single-player into the online world, and fleshed out.