The current Apple GUI is wonderful - are you high? I'd rather use Windows.
The GUI is very tired - in what way?
Cineroma will exist, the problem is how will it integrate into other apps?, Acorn spent time getting Replay 3 ready with the ability to play other formats via plugins, instead of having to have an image filing system to convert them to replay format, but that work seems to be lost.
In the end of course we'll have to run via linux, new apps with the look and feel of RISC OS apps, and old apps via emulation, so it would be a good idea to create the RISC OS version of Gnome/KDE/whatever.