Osipova is still going to dance w/ ABT at the Met Season; how many performances I don't think anyone knows yet (I know some folks discussed on an early page possible conflicting seasons with ABT vs RB, but I haven't been able to find them). She never danced in ABT's fall season but did tour with them - and how her tour performances w/ them will be affected is I believe still not certain.
I don't think it could ever be a black or white win-win-win - what is a "win" for another dancer getting a new opportunity isn't necessarily a "win" for ABT. If she doesn't perform that much w/ ABT starting next season, then of course that opens up opportunities for others (seasoned principals and/or soloists), but she is arguably the biggest box office draw right now for a ballerina so ABT won't necessarily "win" if her performances become very limited with them.
Not sure which principals you're referring to as "many of whom are leaving or have left"? Not many have left recently - not females anyway. A lot have cut back on their performances w/ ABT as they have other company obligations now (Murphy), or due to age or impending retirement (Kent, Dvorovenko). But, promoting new talent is something that remains illusive at ABT - well, rare is probably a better way of putting it. Osipova performing less often w/ ABT certainly won't directly translate into a soloist getting promoted to principal. It might help. But, ABT can also go out and get yet another female principal guest artist (or permanently hire one) from another company to fill in for roles Osipova would normally perform, thus removing opportunities for a soloist (and one who needs that opportunity in order to get promoted).
Evgenia Obraztsova would be a terrific replacement if Natalia O. decides to leave ABT for good.