We learned not too long ago that Siri is on schedule to speak a few more languages soon, specifically Mandarin Chinese, Russian, and Japanese. Siri herself (itself?) has confirmed that at minimum Japanese support is coming soon, according to 9to5 Mac. I personally verified that asking Siri "What languages do you speak?" returns Japanese as a result, along with the English, French, and German that Siri supported at launch in October 2011.
Despite what Siri says, however, Japanese is not yet showing up as an option in Siri's languages settings. Full support for Japanese and any additional languages will likely require an iOS update. With the last update to the iOS 5.1 beta having taken place more than a month ago, industry speculation points to iOS 5.1 getting its public launch alongside the next-gen iPad, which we expect to see announced in early March.
Apple has committed to increasing Siri's linguistic capabilities in 2012, with support for Spanish, Korean, and Italian expected later this year. Sadly, it appears Siri still has no love for the Scots.