The implication of the Std. namespace is that all such "standard" libraries will be distributed with all Haskell systems. In other words, you can rely on a standard library always being there, and always having the same interface on all systems.
What's about version changes? How can anybody garantee that a library is stable? Some functions or instances may become obsolete or even disappear. Other may be needed in later versions of the library.
We can't provide absolute guarantees of course. But this is no different from the situation with standard libraries in other languages - witness the difficulties with libc versions etc. I think the best we can do realistically is to aim for maximum stability. In some cases, it may be sensible for a new version of a standard library to adopt a new name, simply to make things clear. We should probably decide this on a case-by-case basis if/when the problem arises. Regards, Malcolm