Actually, since the law has been announced i have heard of a lot of retail stores/hotels in japan accepting bitcoin or planning on doing so in the near future. Even if merchants don't pick up bitcoin, as i said it's still an added incentive for investors to invest in btc in japan.
Between company x announcing to accept Bitcoin and actual usage is still a world of difference. Point of sale usage of Bitcoin has been sobering so far, at least anecdotally. But who knows, if Bitcoin "clicks" with Japanese culture they may just very well improve on the point of sale process.