Cars overall depreciate on the scale of 10/15 years or so. Right now the depreciation rates are the same. It's an interesting artifact of ICE vehicles that people don't expect any car's drive train to last more than ~15 years. It shouldn't be a surprise that car manufacturers were skeptical of battery tech right up until they hit about that same magic lifetime number. It also shouldn't be a surprise that car manufacturers won't have a lot of incentive to push it past that magic lifetime number, because that would affect car replacement rates and that would affect the bottom line.
Mostly battery replacements look to keep the used car / secondary markets busy, and if we expect to see interesting innovations in battery replacements that's probably where we'll see them as more electric cars get resold to secondary and tertiary owners. (Just as we see the used car markets pushing innovations in after-market parts in general.)
You are right in that maybe leaves room for a disruption that someone might be interested in a "car for life" model where electric cars might be built far more sustainably with an ideal towards larger reuse of the vehicle over the owner's lifetime and a larger depreciation scale on the order of multiple decades.
That would be a huge game changer, and would potentially be great for the planet (less steel production alone, conceivably). It would also take a lot of work to make it happen, given the existing industry reliance on the current business model for most of a century now. It would also be one extremely huge disruption in so many downstream industries, secondary markets, etc, to the point where it may be more of a revolution (in the industrial sense, but also perhaps the war sense) than a "simple" disruption.