I fully agree with Bill on this one. It's actually pretty useless to have X different interfaces for notifications. We need an abstract interface for it that hides the actual implementation.
There isn't all that many variants of file/directory notification APIs, so it shouldn't be too hard to dream up an abstraction. You pretty much need a method to query if the system supports file and/or directory notifications. Then you need a couple of methods to (un)register callbacks when objects in the filesystem changes.
If possible, it would also be nice with an even higher abstraction layer, that always allows the user to watch files, regardless if the underlaying implementation supports it or not, but that can wait a bit.
As for comitting things to 7.8, it's not a big deal if it doesn't break current APIs, but I'd wait until we got 7.9. It's not too far off.