There will always be people around repairing batteries for things that are worth using. Replacement batteries for the major brands will be available for a long time, and there are plenty of electronics nerds who will be fine repairing batteries for more niche products. Heck, you can already get adapters to use any of the major power tool batteries with a Dyson vacuum

I wish that there were commercial applications for cordless vacuums because that's where you really get robust long term support (at a steep cost though)