I agree completely that Japan is at least 8 to 12 months ahead of the closest wired country. In the GSM world, GPRS will not rival current DoCoMo and CDMA One speeds until mid- to late next year. As you stated, the US is slow to deploy the latest technology due to balkanization.
The problem that I see with converting all these Japanese wireless subscribers to wireless consumers is the byzantine Japanese credit card system. Japanese banks have never led the way in innovation. Will they suddenly do an about face now? I see this as a big stumbling block.