BMW Blog has an a post on this now, too.
http://www.bmwblog.com/2015/10/22/bmw-i ... w-battery/
With regards to range increase, I think we will be talking about an improvement in the region of 10-20%, not more. It will provide more than enough to keep pace with the next Leaf and Bolt (for which we so far only have manufacturer's range promises), but nothing beyond that.
In terms of retrofits (and if these will be offered - a BIG if), the next big question is how much BMW will give you as a trade-in. In general, dealerships will be keen to once again get customers on the phone and through the door, reengage with them. BMW on the other side may decide to simply offer the extended battery as a new model or an extra. My guess is that the latter is more likely.
Unless the potential range increase is significantly higher than 10-20%, most REx drivers will pass on a potential battery upgrade, as they parted with more money and already get decent mileage if needed, albeit burning fossil fuel. In my mind, the main target market for a battery retrofit are the BEVs, which may be able to get a boost to a 120 mi real-world range.
If however this new i3 2016 evolution includes more fixes and updates than merely the battery, then an interesting upgrade cycle might emerge, as many lease deals will end by late 2016.
One problem that Krueger might have created for himself now is that i3 sales may be hampered or damaged for 9-12 months, as people will either wait for the next model and go elsewhere. An announcement in January of Feb 2016 may have proved wiser. Dealers (particularly in the US, where stocks appear to be high) will have to adjust prices. This could end up as a i3-deal bonanza, who knows?