I am reasonably sure that C++ is used to a great extent when developing the player application. There is some ARM assembler in the visuals I think, and possibly in the audio decoder engine, but for the most part, you're looking at an application written in C and C++.

Whether or not the Mk1 owners get left behind is a good question. Having ethernet on the Mk2 certainly simplifies things for a lot of the coding related to transferring files to the player, because you could just use FTP for that. If you want to implement USB for the Mk1 owners, then you're probably talking about a system whereby the user-written player has to work with emplode over USB. As I said, this is probably do-able, it's just more work.

The Mk1 owners also might benefit from the project discussed here, something I'd still like to see happen.