That's all very interesting news, good to hear.
On the 'inevitability' angle, I think that is a matter of opinion. For instance, it is easy to forget that Xine is just another of those "embedded apps" and this is completely transparent and appears to be completely a part of the Orbiter. This, of course, is achieved by using the library implementation of Xine rather than the Xine GUI application, and so you can show as much or as little as you wish allowing you to wrap it completely into the UI... note, without having to bring it into the Orbiter.
Theoretically, doing the same with either VDR or Myth is entirely possible if those respective projects also built "lib" implementations of their projects rather than just complete applications with UIs. The drive for the Xine project to do so is obvious, but for Myth I guess its not really a big issue for them so unlikely to happen!
Will have to work towards switching to Myth!