yes there are quite a few but you will find that quite a lot of them are based on Debian (e.g. Ubuntu, Linux mint...) or others (such as Red Hat).
I'd say the Ubuntu has the support that is needed for a large distribution and can basically support most things now, so I say it has happened. Of course people will always want to use different software to do things and so there will never be a unified front, but that's no different to windows.