I think some of the examples are not what I would consider as iconic roles, e.g., the Urinetown cast, all of whom were wonderful, but iconic???? I also don't consider the Fun Home roles / performers as iconic, but I accept that that will be controversial.
Definitely Nathan Lane in The Producers.
Cherry Jones is too old to play The Heiress, which would constitute an iconic performance...maybe Doubt, which is arguably an iconic performance.
Maybe Hugh Jackman -- who I think gave an iconic performance in Boy From Oz -- but I doubt that he'd want to do that and, let's face it, it is not exactly much of a show. You would like to think that the show justifies revival itself.
Wicked is probably not going to close in my lifetime (I am 67), but I imagine Chenoweth and Menzel -- who represent an iconic team of sorts) could pull it off for a while yet, (the green cosmetics would help with Menzel; Chenoweth is unique and, aided by the right make-up artist, could pull it off.
I suspect that Miranda and Odom could come back in 15 years and get away with it. (The revivals identified were 10 - 20 years after the original opening...even Channing did her first Broadway return 15 years after the original opening).
Harvey Fierstein could definitely do Hairspray for some time to come, with all the makeup to cover his aging.
I think Cynthia Irivo's performance in The Color Purple will be considered iconic; given her current age, she could probably still get away with playing Celie again in 15 years.
Then there is the unusual and probably unique case of Bebe Neuwirth, who came back to Chicago, but not in her iconic role. Make it a footnote.