My prediction? Launch is Q4, with Founders' cars being delivered before EOY. Those cars only go to the people with a vested interest in Tesla and very close, very loyal to Tesla. Elon, board members, major investors. The people who are not going to go to the press and spout off about problems on early production vehicles. Then, as always, there will be a few months lag as Tesla sees what real world issues there may be on those vehicles and they make corrections to the production line. Molds are fine-tuned, part specs are updated. Then the Signature vehicles will be produced and delivered.
End of Q1 is what I'm planning on for Signature #2.