So, I'm actually the script editor for Operation Abyss and hopefully I can clear up some misconceptions about the reasons why this title lack dual audio.
The one thing that keeps going unmentioned in this discussion is that Operation Abyss is actually two full length games from the Generation Xth series crammed into one Vita cartridge, which takes up a lot of space. Unlike the Vita release of Danganronpa 1 and 2, the option of separating the games into two cartridges to release them them separately was not made available to us. For this reason, there was only enough space on the cartridge to accommodate one voice track. Since we specialize in localizing Japanese games for English-speaking territories, we decided it would be convenient for our English-speaking audience to localize the text and voices into English.
Regarding our policy toward dual language releases, it has not changed. When we have the ability to release a title with English and Japanese voices, barring extreme circumstances we will do our best to provide that dual-audio experience to our fans. If we do not have that ability, providing an English voice track will always take precedence over providing the Japanese voice track, but only if we have the budget to go to the very expensive trouble of recording English voices in the first place. If recording voices is not an option for a title, then we'll release that title with localized English text and the original Japanese language voice track.
Hope this clears things up.