Uhm, pushing your own agenda much?
"The OX plan is more subtle, and entails extending IMAP (b.1986) to create secure, authenticated group chat. "
As others also stated: why IMAP? My theory? To enforce this whole idiocy onto people. Dovecot is a pretty popular e-mail server and this way you can more or less force this new "standard" onto users without them even realizing it. It'll be much easier to persuade people to use something new if it turns out that they already have it installed and don't need too much extra effort in comparison to trying to motivate people to install something new.
Instead of changing existing current protocols and risk generating more gaps between services (do we really need multiple IMAP protocols?) why not try to come up with something new instead?
Or better yet: try to elevate an already existing design and make that yours! That's what open source and open standards were made for, is it not? And there are dozens of projects which try to utilize chatting and communication services.
Alas... I read about this before and as a result we removed Dovecot from all our servers and replaced it with Cyrus IMAPd. Despite its name it supports IMAP, POP3 (and the encrypted variants) as well as smpt and lmtp. The best feature, in my opinion, is that this project has no ambitions into creating the "next big Internet hit" but instead focus themselves on what they're good at and which really matters: providing one heck of a mail server!
This may sound like a negative rant to you but if you look at Dovecot's history you will notice that it has "change because of change" written all over it. Take for instance the sudden configuration format change: from one easy to administrate config file (well documented and well segmented too) into the conf.d crap which it is now: dozens of different config file parts, and good luck to you in guessing the right file(s) and section(s) to edit! And why? How exactly enhances this my administrative experience? Wouldn't it have been enough to merely provide an include feature and (here's the big one:) let me decide if I want a one or multi -part config file instead of shoving it down my throat because you needed something "new"?
Yes, I'm aware that I can revert back myself. That's not the point: because after every upgrade you'll be force to go over the multipart crapola again in order to check for changed and/or new parameters and options.
And these are the people who now want even more shiny new stuff in the form of IMAP socialized media? Pardon me for not being a believer here ;)