The DITA standard does not place limitations on what languages are supported. The only limitations are those placed by the tool or vendor you are using for DITA support.
One example of language support from tools is with generated text - for example, a caption that automatically begins with "Table #" before or after your table.
Another form of language support is in the actual translation of content - if you use a vendor to translate your content, then they will generally support translating to a specific set of languages.
In short, when considering language support in DITA, you should only need to determine whether your translation vendor supports translating DITA to your desired language, and whether your publishing tool supports converting that translated file to any required publishing format.