I think that either Sonoma will turn out to be the last version of macOS to have an Intel build (most likely), or macOS 15 will be. In the case of the latter, I don’t think macOS 15 will support fewer Intel Macs than Sonoma does. I don’t really see the justification/benefit of cutting more Macs unless you are going to make the sort of changes to the OS that wouldn’t be worth doing right before Intel support is dropped anyway. Meanwhile, it would feel really weird justifying the Intel build - which has to be an enormous amount of work - only to support it on so few Mac models. Maybe they might do something like that for PR reasons, since it would make the drop of Intel support appear more soft and less abrupt to the public, but I don’t think they’re overly concerned about that perception anyway, so that seems pretty unlikely to me.
No way macOS 16 supports Intel. It will probably still have Rosetta 2 though - they are clearly nowhere near as eager to dump that as they were with Rosetta 1.