Perhaps he means it won't affect the franchise because the franchise is effectively canned at this point anyway? It's an awfully pessimistic way to look at things but at least he'd be accurate.
Given that it looks like AAI2 made more of a thump than a splash in Japanese sales compared to the first, I doubt they'll believe it worth pursuing a third game in the Kenji subseries. They could continue where they went with 4, but...despite the high sales (which I would largely attribute to being the first "real" DS game of the series) people haven't been very fond of it in retrospect and I doubt that a straight-up GS5 in that vein would somehow revitalize interest in the series. The third option would be going in some other completely new direction but that's no more likely to attract people that have passed on the franchise thusfar and raises the risk of being too 'new' and turning off the pickier of the current fans.
I don't like to look at it, but if the treatment of Devil May Cry is an indication of Capcom's shifting battle strategy (i.e. it sells decently well but isn't a megahit, so drastic change is called for), my fear right now is that they don't see enough hit-value in the Attorney games to warrant further development on any major scale, much less undergo the expense of what's probably a more difficult lingual localization than most games. As much as I don't want this to be the case, let me stress that, it's possible at this point that Gyakuten Saiban could just be...over.