We have a MS now and down the road need to replace a second car I mostly drive around town and for local errands. I thought maybe hubby would go smaller and less expensive for that one (as in M3) but we both love our S so much we could see maybe getting another S with bigger battery and keeping the 75D. Still probably a bit down the road but we've been very happy with our MS and would love to stay with Tesla.
We tend to stick with a brand car as owners if we're happy with our cars. When we met we both had Honda Accord Lxs, those eventually got replaced over time with a Toyota Avalon and a Camry, so two Teslas wouldn't be surprising. Having driven our MS I don't think I'd ever go back to an ICE for a multitude of reasons that never seemed to matter much to me before but do now.