This is actually really interesting and I support this.

To be fair, purely in profit statistics, Germany and France bring in the most revenue in the gaming industry over any spanish speaking country. But this doesn't mean the game doesn't have a large spanish speaking population. SE just has to see if it's worth the cost and if it has enough profit. At the end of the day, it is still a business.

As a developer, it no doubt gives me sweaty hands to think of such an undertaking with a game this massive and still maybe even an expansion or two in the works. Knowing SE, I don't think it's in their habit to do things half assed for lack of better words: they would want the language done in full (text, UI, voice acting, advertissements). Which would be cool because immersion is a way to learn a language and it would be cool to learn it.

But I do wonder. Supposing there is a go ahead and knowing how many different types of spanish there are (dialects, regions, idioms, nuances, etc) which would you use?