John, I think his point isn't that the MCU isn't supported in SONAR, but that it won't be developed further. Frankly, open source is the way to go - there are a lot of potential variations in the MCU protocol, and I think it's more likely some user is going to come up with a really useful twist on it than a developer at Cakewalk who is working on new features and bug fixes.
At this point, the MCU standard is pretty mature - the Mackie Control appeared in 2003 if memory serves. If you want to do transport, solo/mute, arm record, and move faders and panpots on your main channels as well as switch banks, it works pretty reliably. Hard to say whether Hypercontrol will be equally universal in 2025.