On Teslas? That’s fairly uncommon especially on newer models. There’s plenty of 10+ year old Teslas that have done hundreds of thousands of miles on the original battery pack and still going strong.
Reliability has only improved since then, especially with the recent shift (in some models) towards LFP chemistry, which is much less susceptible to degradation over time than nickel-based chemistry.
Besides, the Model 3 and Y are very popular vehicles today, selling in the millions globally. So not only will the resale market be strong in coming years, there will be a good supply of low-cost parts (including battery packs) from salvage vehicles. You won't have to go to Tesla for a replacement battery back even if you needed one.
The sort of people who used to buy brand-new Subarus are already buying Teslas.
The people who buy used Subarus will be buying Teslas (and other EVs) in 5-10 years time when they're going cheap enough on the resale market.