As far as adoption is concerned, I'm not sure it should be that big of a concern.
After all, D is supported by GCC and Clang and continually being maintained, and if updates stopped coming at some point in the future, anyone who knew a bit of C / Java / insert language here could easily port it to their language of choice.
Meanwhile, its syntax is more expressive than many other compiled languages, the library is feature-rich and fairly tidy, and for me it's been a joy to use.
After all, D is supported by GCC and Clang and continually being maintained, and if updates stopped coming at some point in the future, anyone who knew a bit of C / Java / insert language here could easily port it to their language of choice.
Meanwhile, its syntax is more expressive than many other compiled languages, the library is feature-rich and fairly tidy, and for me it's been a joy to use.