I think that would depend on how much EU citizens care about being fully waterproof. I assume there will be focus groups.
If that is a high priority for EU customers, then it will cause Apple to have to do an entire redesign. If they ended up doing that, then I don't see any reason why they would make a separate US model line. If EU citizens don't care about waterproof and are fine with it being water resistant, then I could see them having a waterproof non removable US version and an EU version that has removable, but is only water resistant.
There is a real risk that the US eventually follows suit, and there is no reason to re-tool twice if you don't need to.
I'm not sure anybody really cares about waterproof. I have a waterproof smart watch, but realistically I'm not going to wear it swimming.
Pretty much every phone that I've ever owned that has died has died not because it was introduced to some water, but because the battery failed. Cost benefit analysis would indicate that a user replaceable battery is of a higher priority for most consumers. And the rest just won't care one way or the other.
Anyway the current iPhone isn't waterproof, it's only water resistant. Very few companies will advertise their phones is actually waterproof in case somebody tries it.
I have a water resistant smart watch and I take it swimming all of the time. I see lots of others swimming with smartwatches too. Smart watches are usually fitness tracker. I very much care that the watch is water resistant. I care more about that than having a user replaceable battery, which I’m unlikely to replace given that I never did when replaceable batteries were common in phones.
Waterproofing isn't important so I can take it swimming; it's important in case I drop it in a puddle.
The battery on an iPhone is good for about 1000 charge cycles (will maintain at least 85% capacity), which is about 3 years of normal use. After that, it costs like $80 to have Apple replace the battery. That's absolutely worth it to me for the improved water resistance.
Not a great argument, it's not impossible to have both. The Galaxy S5 was IP67 and had removable batteries (my favorite phone so far). There is a Galaxy out right now with removable batteries with IP68. Iphones are 67 to 68 depending on the model.