One intervening factor, imo, is that adding support for C++11 is a complex and unpleasant enough undertaking that few volunteers are able to do it, and fewer of those are interested in doing so. I would guess most language/compiler hackers would rather hack on something other than the mess that is C++ compilation, if they have a choice (and if they're volunteers, they do have a choice). So it ultimately boils down to what companies want to do, since many enterprises are heavily invested in C++. If someone pays their employees to contribute support for GCC, it'll get done, and otherwise, it's less likely. Not that much different from the Clang situation, where C++11 is only really getting implemented because Apple cares enough about getting C++11 support into XCode to pay for it to happen.
don't underestimate the capabilities of `volunteers', or floss developers; nearly 30 years of apple software was thrown away again and again, and apple jumped to something new without much backward compatibility. So, they enabling sophisticated development by paying is a temporary illusion.
Are you referring to the move to OS X? Apple ran the previous operating system within the new operating system just to run those old apps, and Carbon was provided as a transitional API for many years. I'm not sure what this has to do with anything, really.
A backwards compatibility argument (whatever it may be) doesn't make sense here, as Clang has been designed to be backwards compatible with GCC-based projects.
