No, 5-10 years is reasonable. Quite possibly on the lower side of that estimate. There are a LOT of retirements coming up in that time frame. Of course, if the whole world falls over with some crisis of some sort then it’s anyone’s guess but that goes without saying I think.
edit to add ; it also depends a lot on where in the 90 new hires you are. The first newbies taken on of course will be more senior and therefore several years closer to upgrade compared to the guys at the back.