Call me crazy, but I think the final release will actually surpass the last gameplay showcase in a lot of ways.
Rockstar is nothing if not consistent and predictable, they follow this exact pattern with every game. They show off an older, rougher build in trailers, then polish it up significantly by the time it actually launches. We saw it with GTA V, we saw it with RDR2, and I guarantee it'll happen again with GTA 6. Mark my words.