I agree that VW will probably not have the option of upgrading batteries should new tech become available, although it might actually benefit them if they were to announce such a program because that is the one hesitation I have to buying a new EV. Unfortunately, my commute does not make a lease practical. If they were to offer this, it is one less worry and people could buy with confidence that the car won't lose a lot of value as the tech improves. Clearly they would not offer a new motor but batteries are seem like they should be an upgradable item.
Could a third party provide new cells? I suspect that the batteries have to be serviceable. It would have to be custom built for the car and there would have to be enough e-golfs to make it worthwhile for a third-party company to do this. I wonder how practical this would be.
Actually, that is another question, the battery is warranted for 8 years, what happens after that? Can you buy a new one with the same specs?