We don't have plans to support the LINQ technologies in C++ in the Orcas release. We haven't ruled out supporting LINQ in a subsequent release. When/if we do LINQ will depend in large part on customer demand for the functionality.
VC++ has a vastly larger product surface area, a great deal more history to consider, and much greater complexity of technology than C# or VB. And VC++ most devote resources to native code as well as managed, not to mention interop technologies, the C/C++ libraries, etc. The simple answer to your question as to why C# and VB seem to innovate in the managed code space more quickly is because it is easier for them to do so.