"we could stay close-to-the-bone C++ design, making those 99% of C++ developers a lot more happy"
Are you kidding? Writing in ISO C++ sometimes can be pain in the * compared to managed languages. C++ is just too low level for GUI development to be comfortable with. The more features from managed languages we have - the better.
I sincerely hope C++/CX will be standardized and consumed by ISO C++ to make all C++ developers' life easier.