Yeah, you're right, they're not going anywhere as well, they're just so niche, a lot of people would probably spend their entire lives without seeing one.
The A battery has been obsolete for a long time now.
C, D, and 9v are on their way as what's left of their dwindling niche use cases that are progressively being replaced by rechargable ones. Think of boombox, or flashlight. Maybe the 9v is still solid for something like multimeters, and I've seen that automatic room sprayer with C or D batteries.
For AA and AAA, tho? They're not going anywhere for a long time. Even when all the flashy fun stuff all have their batteries in Lithium, or whatever comes next, a lot of the boring stuff would still be having them. I have this portable microphone I got from late 2010s that still use AA, and so are all my wall clocks. Also, there are good reasons why the walkie talkies have them as options.
Some rechargable forms have become universal now, like the 18650, but I think they won't replace the smaller ones.
Let's face it, even if he managed to get it working for himself, he'd still have to fight to get it adopted. The way I see it, most people won't care and simply think it would be too much of a hassle to switch to anything. The ones who do care cannot wait to have everything in IPv6.
Herbal ones are options too. I could definitely do away with some iced chamomile or chrysanthemum tea. Just make sure it's completely herbal and it won't have real tea in it.
potæto, potáto