Many of Take-Two's top brass often discuss their games at Cowen & Company conferences and company president Karl Slatoff recently spoke about DLC plans for Red Dead Redemption 2 in New York. Since these aren't press events meaningful confirmations shouldn't be expected, but we do gain some measure of insight behind the scenes.

Rockstar Games has an interesting relationship with DLC. Historically speaking, they were more invested in larger but less frequent single-player expansions, like the two episodes for Grand Theft Auto 4 or Undead Nightmare for Red Dead Redemption. Multiplayer DLC for RDR was also present, however in a smaller capacity.
Come GTA 5, the game's Online component started receiving a steady stream of free DLC. Though officially announced soon after release, no story DLC for GTA 5 was ever released and over the years it became apparent that it got quietly canceled behind closed doors.
GTA Online, however, continues to receive new content and many blame it for the cancellation of the singleplayer DLC:
The question of how Red Dead Redemption 2's post-launch content support will look like has been a hot topic among fans ever since the announcement.
Based on GTA Online's model, it is clear that a steady schedule of free DLC is extremely profitable for Rockstar and Take-Two. However, the core fanbase still prefers single player content and is worried that Red Dead Online will get all the attention.
Karl Slatoff's comments regarding DLC are diplomatic and inconclusive, likely because the company has laid out an announcement and promotion road plan that doesn't include a primarily finance-oriented conference event which gets minimal reportage.
Across the board, we do see downloadable content as an interesting business model for us. It depends on a game-by-game basis whether that makes sense.
Rockstar has specifically said that's something they would contemplate in the future but hasn't made any specific announcements about Red Dead or any of their other games going forward. It is a very lucrative model for us; it is a very compelling model for consumers because it allows them to continue to engage in the game in a way they are used to engaging with the game.
Thing is, the way he words the comment it seems more focused on multiplayer DLC.
The success of GTA Online's DLC in keeping players coming back for more and engaging with the game's microtransaction (or "recurrent player spending opportunities" as Take-Two calls it) system are well known which might explain the "very lucrative" description.
Statistically, the singleplayer expansions of older games were unfortunately quite the opposite of lucrative.
The popularity of Red Dead Online will likely determine the future of the game's post-launch content. Prior to the release of GTA 5, Online was expected by Rockstar to be a minor element of the game with little success that would be forgotten in a couple of months, which is why single player DLC was planned, but then the explosive success of the multiplayer mode reshuffled their priorities. A similar shift may alter what gets focused on with Red Dead Redemption 2.
Rockstar has promised to reveal more information about the game in the coming weeks, so we might learn more about what to expect.