resale values of aging models could continue to see notable declines
No. Not 'could'. 'Will'.
Every Model S owner should have known he was buying into a new market segment of real world usable, larger electric sedans. The (big, sometimes more, sometimes a little less) premium you paid for that was the entrance fee for the ownership of such a car. It was high, and higher (bigger) when Tesla needed more cash and was able to squeeze out more.
It STILL was worth to join the party early, as we got the pleasure of already years of miles driven electrically.
But I have zero understanding for the people complaining about a Model S losing resale value. This is not an investment. It's the price for a good used daily (if you want), and for a tool.
Who did not take into consideration that future models would be better yet cheaper made a mistake.
(I am entitled to be that harsh because I am in that boat, to some extent. I paid cash. Even when Tesla offered bad rates and low residual leasing, that would have been the better - no, about equal - deal. In a hindsight, buying TSLA stock... blame me)