Even delivering 350,000 vehicles in 2018 will be a huge stretch - Tesla only delivered 76,000 vehicles in 2016, and I believe they are aiming for around 100,000 in 2017. Jumping up to 350,000 is a huge jump and not easy to do logistically - it isn't easy to grow any company that quickly given the increased requirements for labour, logistics management, etc.
There can be a few other factors at work as well:
- What options do you plan to have on your Model 3? Tesla may prioritize Model 3s that have all of the bells and whistles and provide more revenue, and a higher gross profit margin, than more basic models. I ordered my P85D shortly after the D was announced. If you wanted delivery within three months you needed to get the P85D - delivery was much longer on the S85 or S85D and you needed to get air suspension. I didn't care about getting air suspension so that wasn't in my config - but they called me and said that if I didn't want Air Suspension then my delivery would be pushed back from late December to March.
- Tesla may prioritize getting models to the US market first since that is their home, and by far, the largest market and the one watched most closely by Wall Street analysts. Canadian deliveries may get low priority.
- Production runs - I don't know what is involved in switching over the production line to produce Canadian vehicles. Maybe it is nothing other than different airbag stickers and software but they may not want to bother with having to switch over the production line if it does entail some down time.