Can't tell. Some sites say that it will only be 8 and 16GB in the USA, but I saw one site that was taking pre-orders that had the 64GB listed, but no price, just a question mark. Not sure what that meant, but figured it meant not sure if coming to US at all. I would not buy the 64GB model because I am only using mine around the house. But, if Sony offers a 64GB model, if I want I can send mine back and order that one with the same great financing deal (no interest spread over 12 months). That is, if they offer it before 30 days.
Hopefully they will do the 64gb for you, can never have enough storage even if for just round the home ; )
If I remember rightly the X in the states only had 16gb model to start with and it took quite a time for the 32gb to finally reach your shores, so will most probably be same scenario again.
Did the A846 come with a plastic slot cover for the Sony charger/sync docks by any chance?