There will be 4 nominees for Musical Revival.
There are 6 eligible shows, which yields a guaranteed 4 nominees. There would need to be at least 9 eligible productions in order to yield 5. With their new-ish rules around ties, we could technically see a 5th nominee in this category if there is a tie for 4th place.
I would personally swap out The Wiz for Gutenberg in your 4 predictions. Gutenberg was loved all around, while The Wiz will likely only be praised for its performances, but receive some harsh critiques for the "bus and truck" production values.
I continue to think there will be a tie in the Best Musical voting and we will see at least 6 nominees, instead of 5. I think Illinoise, Suffs, and The Outsiders feel like the ones with enough buzz to maybe win. Then the other two slots are near impossible to figure out. Hell's Kitchen, Here Lies Love, Water for Elephants, The Notebook, Days of Wine and Roses are all within striking distance (maybe Gatsby too? Haven't caught that one yet but heard "meh" things. And I'm not expecting great notices for Lempicka today...then again critics have gone opposite my expectations for most shows this season). And the rules state that for production categories, ties for the last place slot only need to be within 10%, not exact ties. With opinion all over the place this year, it is incredibly likely that the shows in 4th, 5th, 6th, 7th, place might all be within 4 or 5 overall votes of one another.