Quote Originally Posted by Ansla View Post
That's completely up to the distribution to decide, there is nothing stopping them to distribute libstdc++5 forever, this is exaclty what Microsoft does to preserve backwards compatibility in Windows, they ship dlls from old versions of their SO until they consider it no longer makes sense to do so.
Plenty of things break even without soname change, though. Try running any older Linux game & seeing if it runs - Alpha Centauri, Uplink, etc, they'll all crash horribly due to incompatible changes in libraries which never bothered to bump their soname.