No business case? I'm just staring to read deep into IP6 I don't see much negative in there. And correct me if I'm wrong here but with an address space that big every damn thing on this planet many times over can have a global IP address. Google would have a field day with that type of stuff.
There is like a billion addresses available for each person on planet earth and if they wanted to my jeans could have an IP address assigned to me.
Basically it comes down to don't fix it till it's broken. I expect sheer panic in all news media in about two years or so.