We don't yet know what the long term demand is going to be for the Model Y. This early batch of cars has included a good few Model 3 owners who always wanted/needed a hatchback and who have been closely following the development and release dates in the UK. The lack of Tesla advertising probably means that there are a lot of potential new customers who are not even aware of the Model Y option yet. My bet is that there may be a a very brief softening of relative demand (still high but not stratospheric) before a slow and continuing increase as the Model finds its place in the awareness of the car buying public. I have no crystal ball about Tesla's thinking as to whether they will introduce a SR version soon but I'm not seeing anything that suggests there is any great pressure for them to do it at the moment. If they think it's important to do it they'll do it. I don't think the company's fortunes will be much different either way.