While standardization would be nice, I can still order batteries for the Samsung phones I've used 15 years ago. Availability might not be that much of an issue with larger brands.
There's an aftermarket for phone batteries. They're new batteries produced by what I imagine are unaffiliated manufacturers. As long as the phone is popular enough, there should be enough market for manufacturers to make new batteries.
I'm not sure which I like more: A no-name lithium polymer battery going through its chemical charging process near me every night while I sleep, or a no-name lithium polymer battery doing the same thing somewhere else in the house every night while I sleep.
Both seems pretty non-ideal if it decides to go exothermic and start a fire. Neither will be actionable (what, I'm going to sue a nameless company in China?).
I am sure of this: Until this battery chemistry is sorted out to be unilaterally safer (which may never actually happen), or we switch to something else that is safer, or third-party manufacturers start bringing their face to the table instead of deliberately hiding in the shadows, I'm sticking to batteries that are sold by the company that made my phone.
I don't have room in my life to save a few dollars by buying cheap lipos from unknowable sources. There's too many corners that can be cut to save on process expense and QC, and they far too often are cut.
And to that end: A standard, legislated promise of 5 years of availability from sounds a lot better than what we have today.