A statistics page is in the works (probably after v1.2.0 is out) but that won’t really help us much for the purpose of adding new languages.
We could see which language people are using among the existing languages, but this can only tell us about existing languages.
We could see which country people’s servers are hosted in, but this has basically no correlation with spoken languages. For example ClassicPress official servers are in Germany and the Netherlands if I remember correctly.
The best way we currently have to look at this is by asking our community members. Last time we did this was in December and we haven’t fully acted on that information yet: Call for volunteers to translate ClassicPress