With JMAP becoming standardised  in the relatively near future, does the runbox team expect to integrate this into there service?
JMAP was created to make something faster and more efficient than IMAP.
In the webmail we have never used IMAP, rather we used MySQL up to Runbox 6 and for Runbox 7 we use a server index and a local index to really speed things up.
We use Dovecot IMAP servers. If they will start supporting JMAP, then I am sure we will be happy to support it for JMAP/IMAP clients. It seems they have been working on it: https://dovecot.org/pipermail/dovecot/2016-November/106262.html