If the album was the first 8 tracks, Starships, Va Va Voom, and Fire Burns, the album probably could get into the 70s. But there's too much repetition in some of the pop songs, Stupid Hoe has an awful reputation since the music video, as well as the fact that people probably are concerned about hip-hop Nicki being shut out due to her discovering her success in pop.
I love the album, but after hearing it in full, I realized my initial assumption of high sixties was wrong. I think it could stabilize once it gets 20+ reviews towards the high fifties and possibly stop in the 60-62 range. Unlikely though, sadly enough.
Oh well. At least reviews almost never affect commercial success.