Does the map reveal as you explore?
Yes. Unvisited areas stay hidden until you reach them.
Rockstar North says new areas are drawn onto the 3D map as they are unlocked and explored.
The evidence
Visible in official footage; wider behavior may remain unconfirmed.
FamitsuFamitsu interview with Rockstar North co-head Rob NelsonEL PAÍSEL PAÍS visits Rockstar North for a GTA VI demonstrationRockstar GamesGrand Theft Auto VI official siteRead the full supporting guideWhat would change this answer?
A final map interface demonstration or launch behavior.