Don't forget WOD!
Not a giant megaproject like the others, but definitely on a larger scale than a typical mod.
Maybe somebody will pick it up. Exclusivity is not good, but this will also open doors to someone to step up and try to revive the project.
Though I noticed that activity on HLP in general is not what it once was. There were times when you could expect multiple new posts in the modding board per day, threads also rolled off the front page fairly quickly. There was some movement in nearly every active project. It seems that sometime during my big bout of inactivity, it stopped and now it's more like a few posts per week in modding and project boards went all but silent.
Maybe KSP is to blame?
Actually easier to mod than FS, more realistic and very fun. Seen quite a few people from here on their forums, I also mostly stopped modding FS in favor of KSP. People who did story-heavy stuff started writing books (myself included, though I didn't finish anything big yet). I still do occasional testing and I'm happy to try out anything new that does come out, but I don't play nearly as much as I used to.
Ironically, Inferno is one of the few megaprojects besides BP where things still seem to be happening, although not nearly at a pace they used to. Also, if you count extra-FS TCs, then there's Diaspora and WCS (the former seems to be still going, the latter I dunno). I have high hopes for FoTG as well.