On the other hand, C was given a different name when classes were added to it.
Thing is, adding and/or removing features may have an impact on the implementation, can potentially introduce subtle changes to the semantics of the existing constructs and therefore their behavior at run time, have general performance implications (e.g. due to a change in what optimizations are possible), etc. Is it "the same language"? Not quite. It is a "super-language," at best. If it's 100% backwards compatible, that is (which is not guaranteed).
So? C# 1.0 didn't support 90% of the cool features of C# whatever it is now, not even LINQ, the bread and butter of C# programmers.
Java up to 1.4 didn't have generics, closures, streams, modules, and tons of other stuff besides. Soon it will be getting many more.
Is it a different language for that?