If I may weigh in. A few main points on MDs and why as a user I continue to use them and would be disappointed to see them relegated to a unsupported system.
Number one for me is Cost. An ip controllable HDMI matrix, HDMI endpoints, multiple set top boxes/STBs = multiplying the cost to every-room and every zone you add. You can add 'smarts' to any display with a relatively low cost MD and a remote.
I enjoy the ability to control any zone/room from and zone/room without having to have a dedicate room controller (ie. iPad) in each room. Call us 'old skool' but we also prefer to flick through with a remote rather than always use an ipad, ipod touch etc.
The philosophy of LinuxMCE/Dianemo is the central home control. Not just single point to point but in addition multipoint and the ability to move that media/user experience between rooms seamlessly. This includes the same UI, the same control process and access to all media in all rooms. As well as lighting, heating etc. controls. In your model, the only UI is on the mobile orbiter.
Telecom, Game player and surveillance cameras are not considered here yet within the thread. Whilst I agree that the most used component of the system is media, it is the integration of all these smart home systems in one point and turning any display device into a controller and viewer that got me so enthused in the system.
In having said this, not all times is there a need to have a UI and consistent user experience. I use media players and upnp in conjunction with squeezeslaves and traditional MD to get a mix throughout the home. I would just hate to see them become unsupported.
Food for thought.