Wikimedia Incubator is the place where potential new linguistic editions for existing open-content projects supported by the Wikimedia Foundation have their own wikis. There, they are arranged, written, tested, and proven worthy of Wikimedia hosting. Note that Beta Wikiversity is the Incubator for Wikiversities and Old Wikisource hosts content in languages which have very little content as well as multi-lingual sources. In the future, it is expected that very small projects will remain hosted at Incubator indefinitely.
Before its creation on 2 June 2006, the test projects were here at Meta-Wiki.
To get a new wiki, a proposal should be available on Meta; see Requests for new languages. The decision of this is in the hands of the Language committee.