The current timeline for the release of the new hymnbook is 2026, and my expectation is that all the current hymnals will be rapidly left aside once units get the new hymnals. Personal opinion: I'd pause any purchases of large quantities (or any quantities) of new hymnals, and first try the following. I know we all have hymnals in disrepair, but perhaps you could first reach out to the other units in your stake (or neighboring stakes if geographically close), and get an idea of how many new-and-unused hymnals the different units have in storage. I wouldn't be surprised to find out that there are a few units that have a large box (or boxes) of hymnals in reserve, and if so then it might be reasonable for them to share some of them with you (as it's unlikely they would need to utilize all of them before the new hymnals arrive).
I've been thinking the Church might send out a notice giving guidelines for exactly this scenario, to avoid units purchasing hymnals that then end up being unused and discarded. But again, that's just my two cents, and I agree that having hymnbooks that are in good shape, is important however you manage it.
