Yes, I really hope that JMAP succeeds and applaud Fastmail for taking this on. The problem of course is that there's a huge drag in getting new protocols like these established. One problem is that Fastmail works with Cyrus, but Dovecot seems to be much more popular nowadays. Of course, getting a new protocol into Dovecot is a pretty big undertaking, but I hope they will eventually find the time to do this.