Keep an eye on India for the possible future of DRM. The country has an aggressive program to implement the digital format on mediumwave, shortwave, and even the FM band. It could really accelerate the move to digital...or it could be a massive flop. Supposedly the Indian government is pushing hard to make DRM capable receivers easily available, which will be the acid test.
Brazil is in the very early stages of trying out DRM for mediumwave and shortwave. Apparently part of the plan is to push for the conversion of existing domestic shortwave operations to DRM, thus reviving a dying medium. The national public broadcaster is supposedly conducting some tests at the current time. Of course Brazil is also expanding the FM band down to 76 MHz, so what actually might happen is that most existing AM and shortwave stations simply move into that expanded band, which might solve reception issues...and make DRM irrelevant.
It will certainly be interesting to see what comes out of those two national efforts.
On the negative side, several high powered international shortwave broadcasting facilities in the Americas have tried DRM in the past decade or so. And, as part of the overall demise of shortwave broadcasting, each of those sites has been completely closed in the past two years.