None of the languages in TES are really defined. Those that exist are little more than ciphers rather than true languages, swapping out words or letters without adopting any of their own grammatical characteristics and serving simple as a From-English conversion. Admitedly, that's a step above Star Wars, which pretends a repeat of the same gibberish over and over is an actual language, but still...
Personally, i'd like all the languages expanded upon. But i don't see it happening as anything more than a buy-in game feature, like in Daggerfall, where NPCs just speak gibberish until you've learned the Language. Converting a vocabulary to create a fake language is a lot of work, but creating a real language is something else entirely and typically requires professionals (Tolkien was a linguist and a rather gifted one at that, and N'avi and Orcish both has an entire team of linguists working on them).