Really a question for @tom@feddit.uk, but, If the last update was a guide: new version gets released, another instance (usually lemmy.world as they have a large well-funded infrastructure) jumps on it and updates, everyone waits to see if something breaks and then most of the big instances install it.
I'd imagine, if there was a patch for a critical security loophole, then all the admins would move quickly on it but it'd also likely be quite a small patch so relatively easy to do without disrupting the business as usual.