We've been struggling to get the Xfce Foundation going properly. It is still not registered as an official non-profit organisation in Germany (due to Jannis living in the UK and being busy, plus some bureaucracy) and has been inactive pretty much since its inception.
Due to the last few years of inactivity, an official registration has now become quite tricky, involving new board elections and potentially extra paperwork and signatures to be signed off by notaries. This isn't entirely impossible. However, given the lack of progress, the current bottle neck on Jannis, and the registration difficulties, it may be worth considering an alternative to the Xfce Foundation: joining an umbrella organisation such as the Software Freedom Conservancy or the SPI (Software in the Public Interest).