Anyone know what these are for? They've popped up in the Rename Standard Tabs and Labels as new standard fields with the Winter '13 release, but I can't find anything about them in any documentation, you can't see them in the API, you can't get to them through code... Is this part of a move to Country and State picklists?
I think you're on the right line with with that assumption. So many people have to implement the exact same functionality it makes sense for it to be built into the platform.
I also suspect that another reason for new standard fields will be related to the new geo-location features available; since geolocation of addresses is only going to work effectively with good quality data it makes sense for those fields to be standardised.
The only reference seems to be on the idea for this where the Product Management has mentioned around a month back that they're working on it. http://success.salesforce.com/ideaview?id=08730000000BrVWAA0
Salesforce mentioned during the developer show and tell at Dreamforce that they are going to add state and country picklists and that it was with their internationalization team and it was a big job.
It would/could also involve some kind of automatic conversion for existing data
They are also going to do global picklists in the future too, which by the name indicated that they would be cross object picklists.