I use a 2020 M1 MB Air with a 5K Ultrafine. It's the best of all worlds, even better than an iMac IMO. Here's why: The iMac is not silent, MBA is. I work with laptop open, so I sign in with fingerprint sensor, as well as use it for all passwords and web forms. I don't like the Touch Bar, so another win there. I'm a trackpad user, and using the MBA trackpad while on the 5K is better than external trackpad because of the noticably lower latency. The MBA is incredibly fast. As a developer I am wanting nothing with this setup. Best of all, I can unplug from the 5K at any time and take it with me.
In summary: Don't wait for Apple to make the keyboard you want. Get an M1 MBA or MBP + 5K Ultrafine. You pay a little more, but you get the best of all worlds.