Business Week sure thinks so. They're reporting that Amazon is in talks with Kodansha, one of Japan's larger publishers.
I don't believe it. Wouldn't this kind of a negotiation be under a non disclosure agreement? It's standard practice as a way to guarantee secrecy. I know Amazon has used NDA in the past, and I can't see why they wouldn't do it here.
BTW, so far as I know, the Kindle cannot support Japanese because it lacks the necessary font support. It would need a firmware update before it could be sold in Japan. Of course, Amazon might already be working on the update because they're planning to new markets (like Japan).