The decision was made based on the poor reception to the GTA Trilogy remasters.
Red Dead Redemption

This past weekend, Kotaku shared word that Rockstar Games cancelled plans to remake or remaster games like Red Dead Redemption and Grand Theft Auto 4 to focus on working on Grand Theft Auto 6. Apparently, this decision was made by Rockstar after the poor reception and disastrous launch of Grand Theft Auto: The Trilogy - The Definitive Edition.

A few years ago, Rockstar Games was apparently looking at remastering both the first Red Dead Redemption and GTA 4. Kotaku, by way of "a reliable source," says that the projects may not have been fully cancelled. It is still possible that they will be worked on again after GTA 6 releases, but nothing is set in stone.

Leaker Tez2 took to Twitter to suggest that the projects have been fully cancelled.

It does sound like neither game was particularly far into the production phase. Tez2 says that they were "simply in the ideas phase and remained there for years." Ultimately, the decision to greenlight the remasters for full-scale production just hinged on how well the GTA Trilogy remasters were received and how well they sold.

As for GTA 6, solid information about that seems to be non-existent. Rockstar hasn't officially announced a new GTA game yet, so we're left only with rumors. Speaking of which, the latest rumors suggest that GTA 6 won't be out until maybe 2024 or 2025. Some are also suggesting that the scope of the game at launch will be much smaller than expected with plans to add on to it with post-launch updates in order to avoid crunch.