Judging from the tech specs for iPhone 4, the new iOS 4 (formerly iPhone OS 4), available for iPhones and iPod Touch starting June 21, has the following added language features compared to the current version:
Localizations: Hungarian, Catalan, and Vietnamese
Keyboards: Cangjie and Wubihua for Chinese, plus Catalan and Vietnamese
Dictionaries: Hungarian, Flemish, Catalan, Vietnamese
Voice Control: Danish
iOS 4 is expected to be available for the iPad in the fall of 2010.