*Disclaimer* I don't know if any of what follows is actual, but I believe it probably is.
MDT has probably suffered the same fate as Land Desktop. 2009 was the last release of LDT, too. It has been available for use by Civil3D customers, and, from what I understand, a very few number of overseas customers. But no more LDT's are to be offered, for sale or otherwise, as they are no longer building the code for it.
Sure, you can still run the older versions. Subscription customers are allowed to use the product for up to 3 versions back. There just will not be any more produced.
HTH