While Valve has already confirmed that the first Counter-Strike 2 Major will be held in Copenhagen, Denmark in March 2024, following this event it seems like there will be a rather significant change to when Majors are hosted.
As HLTV notes, Valve is shifting Majors to now be an event in the middle and at the end of a competitive season. Specifically, it's noted that in 2025, we can look forward to a Major between June 9-22 and December 1-14, and in 2026, the Majors will be between June 8-21 and November 30 and December 13.
As these are just the dates for the events, we can likely look forward to more in-depth information in 2024, once the inaugural CS2 Major has wrapped up.