Directly from the mouth of Badspot and Rotondo during their live-stream (not quoted, I'm just generalizing what they said):
When will it be ready for distribution?
Badspot has checked all the agreements and submitted forms, now he is just making sure the game works and is ready for Steam distribution. They are also planning on adding cool stuff, i.e. achievements, trading cards, etc. BUT: Rotondo was more interested in the 'cool stuff' than Badspot was. Badspot thought the achievements might be "utter bullstuff".
Steam Workshop?
Badspot wants this to happen. Although he is not entirely sure it will happen, as he has not looked into it yet. So if it can happen, it will.
Vehicle Physics?
Rotondo has been screwing around with it, but he says the system is "F***ed" but he continuing to work on it
New Engine?
No, this is never going to happen. They are not going to redo 6 years of their work. The closest hope you have is a new version of Blockland. Blockland 2 :0 lol jk.
I realize some of these aren't about Greenlight, but I threw them in anyway. Also, I may have misunderstood something they were talking about, so don't take this as absolute certainty.