Considering how most triple-A MMOs released recently have not been localized into Spanish (at least not at launch) I think it's safe to say that these companies have done their research and have determined that it is not (from a business standpoint) worth it to do a full Spanish language localization (or at least, that it is more cost effective to localize for other languages first). RIFT, SWTOR, FFXIV, ESO, and Wildstar have all been EN/DE/FR. If there was really this massive segment of Spanish players dying to play these MMOs, more of them would be doing Spanish localizations.