A $6K 30Kwh battery may not make sense when GM is able to produce a 60Kwh pack for $8700 for the Bolt. In a few years, the price/Kwh is only going to reduce further....the fact that each EV manufacturer is going down a prosperity route for the battery modules means, long term, you would be stuck with whoever made your EV for battery replacements.
Yes, you are right, Nissan is the only one offering an affordable battery replacement option for people who need replacement batteries.
We do not know for sure, if 200 mile range is where the capacity/price of the mainstream EV will plateau, unless we actually start to live in the 200 mile/$30,000 range/price EV era.
Too many variables around EVs to be able to make a foreseeably wise long term ownership investment in any EV, unless a certain range degradation path on an EV is acceptable to your lifestyle for 8-10 years.
1st Leaf : 2013 SV (2013-2016)
2nd Leaf : 2016 SV (2016-?) acquired - Jan 2016
3rd Leaf : 2015 SV (2016-?) - acquired - June 2016