I wonder if xfce has any funding?
I've seen there was a crowdsourcing effort before. I don't think it could really make an impact.
I don't know what a situation with KDE, Gnome 3, Cinammon or whatever else, are there companies willing to support desktop Linux projects?
In general, I don't know which Linux related projects (apart of Kernel, where Linux Foundation is involved and I stumbled to people from AMD working on radeon open source linux drivers).
Linux Foundation has loads of sponsors: