I didn’t even know the second had come out yet! With a low profile release and (judging by the IMDB rating) a poor reception, why on earth would they want to make a third?
S.Darko doesn’t count as having anything to do with Donnie Darko. Donnie Darko is Richard Kelly’s baby. And it works because of the involvement of the Gyllenhaals. And the magical soundtrack. And the book with the appendix etc. And the website with the kooky passwords and newspaper clipings. And the ‘they made me do it’ campaign by graffiti artists. And a screenplay which works at the screenplay stage. S.Darko has a crappy TV director and a plot which doesn’t hang properly. They haven’t followed the model at all. If the third one has Richard Kelly’s involvement, he might be able to revive it with a little help from his friends.