The value is in removing lines of code while maintaining correctness.
If you find now a compiler in the wild that violates the standard with regard to this define then you can prepend a check against that compiler. I think you'd still win in terms of code removed. We're talking here about a check for C++11: There's a standard-conforming, idiomatic way to do that, that as a bonus is short, simple, and fast.
I think that if a check for support for double right-angle in a template line is useful, it should be served as a dedicated macro. If a check for support for && is useful, it should be served as a dedicated macro. But even then, a macro that checks for C++11 can do its thing without aggregating all these dedicated little packages for specific C++11 features. It can do its thing with less code and less work than that.