I think this coming week there’s a better chance of seeing 15.1b1 than there is of seeing 15b9 or a Release Candidate. And if I remember correctly, the beta profile is for 15 and up, not just for 15.1, meaning we’d need to remove the beta profile to avoid getting it. We’ll probably be on this beta for a few weeks until it’s officially out.
As far as any continued updates to 14 are concerned, we’ve got 14.8 and then 14.9 and all of the point updates in between. They don’t need to back port any features, just any important security updates or maybe some critical fix. They could theoretically support iDevices on 14 for quite some time. It really feels like Apple is starting to understand how things really work in the wild. In our family alone we’ve got two older devices the kids use for games and I can basically just leave them as is and still continue to get security updates. Sometimes people just don’t want to get the latest updates. And now some folks get to have their cake and eat it, too.