Someone will provide aftermarket battery servicing, if the market is big enough (it isn't, most likely. Protip: don't buy compliance cars for long term ownership...)
Nothing stops you from buying a used Bolt (or used EV from Nissan, Kia, Hyundai, VW, etc).
GM extended the battery warranties on Bolts that were recalled by something like 8-10 years.
And given GM probably sells more Bolts in a month than the entire production run of Sparks and has for years now, there's almost certainly going to be a large aftermarket scene for battery repair, just as there is for Priuses.)
I never had any problems with it, and returned it at the end of it's lease because I had started a family, and needed a bigger car. I still get letters from lemon-law firms asking if I need help with a car I haven't had for years.
I have a Spark EV that did 130 miles new, now ~100 highway miles after 6 years.
The warranty on the battery lasts another two years and they don’t make that battery anymore anyway. Replacement car would be a $27K Chevy Bolt, which is much longer range and way more expensive than I need.
I’d love to see a standard battery back that was around 100 miles range that cars would use 1-4 of them to achieve whatever range is desired.
Not to mention a standard form factor that would be available for 2-3 decades to prevent a car like my Spark EV with just 50K km from becoming landfill in a few years.