GTA 6 missions — what we know so far

How many missions will the game have?

Rockstar hasn't released any mission count so far. Any "complete" mission list you see out there (beyond the prologue, once revealed) is speculation or an unofficial spoiler — there's no confirmed campaign content beyond what's already shown in the trailers.

Two protagonists, one campaign

Officially confirmed: Jason Duval and Lucia Caminos are the two playable protagonists of a single shared campaign. The official synopsis describes a "criminal conspiracy" spreading across the state of Leonida after an easy score goes wrong. Whether switching between them is free-form (like GTA V) or more linear/story-driven hasn't been detailed by Rockstar.

Heists

Trailer footage shows Jason and Lucia in heist/getaway situations, consistent with the series' track record (GTA V had a detailed heist system). But Rockstar hasn't officially confirmed a formal "heist system" for GTA 6 with planning stages, scalable crews, etc. — that's community expectation based on previous games, not an announcement.