I sold my 31-year-old Volvo 740 station wagon to get my Tesla S. My 1986 model was the last one they sold without air bags and without anti-lock braking. I was determined to get an electric car for environmental reasons, the only question was which one (I had a deposit down on an Aptera nearly 10 years ago). Hanging on to cars for as long as possible is environmentally appropriate, due to the embodied energy in manufactured items. I'm not at all into the American "disposable culture." However, it had become impossible to get some replacement parts for the 740 -- and when I could not get a replacement for my failed driver-side windshield visor (except for very tatty junk-yard parts), I decided it was time to finally move on.
We are poised at a time of disruption in the auto market, and although Tesla may fail as a firm, I think it unlikely. It is perhaps more likely that we will see consolidation and disappearance of many older firms, as sales decline due to economic pressure as some of the currently "externalized" costs of the ICE model become de-externallized, millenials turn away from the expensive traditional model of individual car ownership, and who knows what other developing trends. The expanding markets in China and India are likely to rely more heavily on EVs than ICE vehicles. The EV is here to stay, and Tesla is well placed to remain a prominent player in the field.
Two trends which the discussion has overlooked thus far:
1) Technology for one of the vehicles most expensive components, the battery, is evolving. As just one example: if UT's John Goodenough's sodium-glass battery pans out, we will have non-flammable batteries that are cheaper, charge faster, and have higher energy density (I'll be able to upgrade my S 90D to an S 270D, come the day I need to replace the battery at my own expense -- and likely at far lower cost than if I purchased a battery today).
2) There are already after-market third-party groups supporting Tesla vehicles (for both hardware and software issues, especially in the salvage market), and this sort of activity will only expand as the number of vehicles increases. It is likely in Tesla's own interest to encourage such activity, especially as it pulls back from support of older vehicles in future.
I have every confidence that my model S will be the last vehicle I own (barring an accident). Will it always be one of the most trendy or fashionable cars on the road? No. Will it still be safe, comfortable, economically viable, and useful for 10+ years? Yes. I'm hoping for 31. Enjoy your Model S, Wild Weasel!