Both have been approached, XFCE didn't seem interested (from what I've heard), Enlightenment people weren't available for a meeting. (I've asked a fellow hacker, who attended the meeting.) I hope that this sort-of-exclusivity doesn't minimize the effort, and that we can get more parties involved in a shared specification process as well. I'm not only looking at desktops, but also at projects such as VLC, LibreOffice, Mozilla, etc.
I think the gatekeeper-style FDO has proven to fail, failed to be revived a number of times, and due to that severely limited our (the Free desktop's) possible impact in the market. I see the results as a good sign, it's certainly more progress achieved in just one meeting than in, say, 5 years before, so that gives hope.
I personally would much rather see a space where those specifications are documented, rather than gatekeepers. What 3rd party developers really need is information which standards they can use, and on what platforms they're supported, maybe something like http://en.wikipedia.org/wiki/PhoneGap#Supported_platforms