Apple tried to do that last year with iOS4 with the same trick to limit choice of the language to only use xCode, but they got very doomed for that and some month later they axed those rules.
So I dont think limit to one language is a really great a idea without a tool converting C++ to C# or open C++ interface in some way. So a long this is not done, I dont see GlBasic to been ported to that platform.
Android, even there is still some "pitholes" with various bugs, I guess most/all would veen fixed when beta status left off. But its only possible to port to that because there exists a NDK which is a c++ based SDK.
I hope Microsoft see the light doing something the same. Not really to open c++, but a least have such of NDK with some C++ interface would been nice too.