Performance Target and 60 FPS Uncertainty
Nelson told Flow Games that the game runs at 30 FPS, though the team still needs to consult its technical staff to decide on a higher frame-rate mode either at launch or in a future update.
The same report noted that Rockstar currently lacks firm details on resolution targets and features such as ray tracing.
Digital Foundry Trailer Analysis

After examining the downloadable trailer file, Digital Foundry concluded the footage runs at native 1440p on PS5 and delivers a relatively stable 30 FPS output, interrupted only by occasional single-frame drops.
Because the provided video itself is locked at 30 FPS, additional frame drops that might occur in the final build remain unseen.
Series Precedent and Platform Questions
The decision aligns with the series history, as Grand Theft Auto 5 launched at 30 FPS on base PlayStation 4 and Xbox One hardware.
Performance on the less powerful Xbox Series S and any enhancements planned for the PlayStation 5 Pro remain unknown.