The actual date of the Trailer 3 is not announced yet, as Rockstar has not mentioned anything. The final trailer (Trailer 2) has been released in May 2025 and it is radio silence ever since. They are speculating that it could come towards the end of 2025 or the beginning of 2026 to create hype before the release, which is currently planned to be in November 19, 2026.
So briefing, probably prior to mid 2026, but nothing official.