I admire the OP's optimism, and I do think they will hit their dates, but there is execution risk. In the past, risk has been because of new tech. With the Roadster and the MS, everything was new and built for the first time. With the MX, the delays were primarily because of the first-of-its-kind FWDs. As far as I can tell, there is nothing new in the Model 3. Even with the "Part 2" reveal with its HUD or magic steering wheel or whatever, if they are using someone else's components (like they do with the MobilEye camera, air suspension, etc), the execution risk is still minimal.
In my mind, the biggest risk comes from their ability to scale manufacturing. Scaling is hard--processes and machines that work at Model S/Model X volumes may completely fold at Model 3 volumes and some supply chain vendors may wilt under the pressure (including the GF). The good news is that this is the 5th production line they are standing up (Roadster, original Model S serpentine line, Model S/Model X high speed line, PowerWall line, GF line) so they should be getting the hang of things. It will be interesting to see unfold and Gilbert Passin (VP of Manufacturing) may be the great unsung hero of this launch.