Qt5 will also get full iOS support this year.
I think, first versions will not be very stable and bug-free.
From my experience, even several iOS screens add too many conditions to your GUI code. Trying to fit in all modern desktops and mobiles at once will be a difficult task.
I personally prefer Mono GTK#, but it's really easier and faster to prototype and make an app for OS X and iOS with Cocoa than trying to play with other frameworks. Also, porting libretroshare functionality to iOS could be tough (I hope my presumption is wrong!).
I'm going to take a look at Qt5 later, but for now I'm thinking RS will need 2 GUI designs (desktop+mobile) and 3 GUI codebases (qt win+linux+osx, ios, android). Since Qt can mimicry Cocoa appearence, I think it is possible to make a nice-looking app for OS X with it.
Still that's a lot of work for a non-fulltime project, so I'm going to start just with instant messaging and then add file sharing.
PS: Also, I have an illustrator in our team (not a professional UX designer, but she has made nice GUIs in the past).