Just in time for me to start thinking about Javascript Promises, comes along an official API, along with a polyfill that basically re-implements rsvp.js with the "official" terminology.
Now for some experimenting (and rewriting jquery.status.js to use real Promises).
It seems from all the discussion that jQuery $.Deferred are not and will not be real Promises, but they can be Promise.cast($.Deferred()) into one. Note that to use that, you need to $.Deferred().resolve() on the jQuery object, but attach Promise.then()'s to the Promise.
Hacking at 0300 : Promises and Event Handers says:
[…] a subtlety in using Promises with event handlers or any code that's executed […]
December 18, 2013, 9:39 am