Well at least on desktop sending files over Jabber seems to finally work fine. So I would say that making it work on Sailfish phones should be also doable, if not working out of the box due to the libraries being +- the same anyway.

Not sure about he state of Jabber voice and video communication (IIRC it is called Jingle ?), but i plan to look into that soon.

Also another are that might need to be addressed are multiuser conferences (MUC) - this was not supported on the N9 out of the box, but there is a third-party application adding that. Having MUC support out of the box would be really nice and could be used for other messaging services that support multi-user communication not just Jabber (IRC, etc.).