I do think 2027 might be the year that JMAP finally gets wider adoption! Between Thunderbird using Stalwart for their hosted product, and the fact that the new agentic tools are very good at writing JMAP integrations, I expect plenty of much better JMAP tooling.

I'm also close to a much more releasable version of the proxy which was first written back in 2014: https://github.com/jmapio/jmap-perl/ -- which can wrap existing IMAP/CalDAV/CardDAV/Submission infrastructure so you can access it via JMAP.