I first hear about this project like 10 years ago. I honestly thought it was just a pipe dream - a proof of concept that couldn't possibly be done. Massive props to the legends who worked on the project.
I'm with you in principle: 99% of these big fan projects never end up finished or released and it's better not to set yourself up for disappointment. Rarely however, they do actually pull through. Fallout: London was a resounding success, and it does actually seem like Skyblivion will happen. Their progress is well documented and they're so close to the finish line now I can't see them not making it.
Ever since I've been acquainted with the project some years back, they've been asking for more volunteers to contribute in order to speed up the process.