This thread is an interesting read. I think an available replacement pack shouldn't be a problem if you have the cash to spend. The bigger problem will be putting an expensive battery into a 10 or 15 year old MIEV.
I bought the car because it was cheap, not because it was the finest EV on the market. We got a barely used one for $10,500 +Tax.
My wife loves it but, facing facts, its a cheap little basic economy car. The only reason it had such a high sticker price is because it has a $20,000 battery in it. Surely over 10 to 15 years the seats and interior appointments will show wear to the point that we'll be ready for something newer. Plus the suspension is likely very basic, so 10 to 15 years from now it may be very costly to maintain and replace suspension parts.
Meanwhile battery tech, new models and designs, will most likely mean that in 10 to 15 years we can move on to an EV that's much better designed, with much better range and style.
Because it already has a very unusual appearance, it will also likely look very dated, 10 to 15 years from now.
Of course, the industry could go the other way. With low gas prices --- In 10 to 15 years we could remember the years of 2011-2016 as the days when car makers dabbled in Electric cars. If that scenario were to play out then, yes, we'll be looking for ways to keep our antique EV's going by adding replacement batteries.
2012 Silver Mitsubishi iMiev ES with QC
2012 Raspberry Mitsubishi IMiev SE Premium with QC
2011 Viridian Joule Chevrolet Volt Premium
2002 Forest River Sunseeker 3100 LE
2001 Buick LeSabre custom
1997 Chrysler Town & Country LX
Blink 240V EVSE