Well, it's in development hell, with the creator making other games in his spare time. If it does get completed, the time involved will probably be comparable to Starcraft 2 or Duke Nukem Forever (the latter of which I am still not sure about).
EDIT: Single-man game developers have a lot to deal with. And the bigger the project, the longer it takes. With one person, the time involved seems to increase exponentially with the scale of the project.