Right now, Tesla has only 2 production lines: One makes the LR AWD & Performance while the other the MR RWD. With US and Canadian demand winding down for those models, the production will be for foreign markets. Until that demand has been exhausted, or a new production line is built we will not see the SR in RWD or AWD form. My best guestimate is the earliest SR will be available in Sep 2019.
And as much as I was disappointed at not getting an SR by 2018, I'm over it now as I realize the cost savings are non-existent when compared to ICE cars as the high up-front price negates any gas savings. And that's without factoring in higher insurance, annual taxes in CT, etc.