While the REST API endpoints were a big goal of 4.5 and won't be shipping with it, there are other features and tickets that should be nice additions. I'll highlight a few.
- I already talked about selective refresh in the customizer, which should be a big hit with plugin and theme developers, and eventually the end user will see a great deal of improvements thanks to that one.
- Joe McGill is proposing an image compression change that sacrifices little but could result in 25% or so image size reductions.
- Ella Iseulde Van Dorpe landed an awesome commit for more additions to inline text patterns of the visual editor. Bold, italic, and code tags will be much simpler. The code one is awesome for me, because I've never had that shortcut on lockdown. Here's a video/gif of it in action!
- Remember the six year old bug report from the issue where a “-2” shows up on the end of slugs, because the post was in the trash when you create the new one (frequent with terms or common pages like “about”). Well, it's fixed! Eric Andrew Lewis drove this home in the end.
- Jetpack's “site logo” feature is proposed for core in WordPress 4.5, and while it's been a contentious debate, it's looking good for going in, I think. There was some confusion about the difference between this and site icons; site icons are for app icons or favicons, whereas this is the tradition logo. There are some proposals for a UI fix by Mel Choyce that help clear it up considerably, and I think this will be a nice feature both for users and theme developers.
- Logging in by email is officially happening! That's a super welcome UX adjustment.
I'm sure there are more things, but I wanted to highlight some that have had my attention. Many other core components are getting iterated on with consistent contributions from familiar core developer faces, and for both them and these folks I highlighted, I'm thankful. It's so easy to drop in and out of core development cycles, and I'm always amazed by the contributors that really stick with it week by week, often for many years.
I hope everyone will be ready to test beta 1 over the next week or so.