I don't think there's really a way know that until they start releasing some names (unless you're in the camp that believes that Japanese VA > all and you're just assuming the English cast will be bad no matter what). I didn't have a problem with most of 1.0's VA. I thought the opening cutscenes were great. In fact, I thought Yda and Papalymo were hilarious. So if they bring back many of the same voice actors, I most likely won't be disappointed. They've really got to nail the GC leaders, however.
As long as it's not as bad as some of Aion's voiceovers where you either got Bill Paxton monotone or overacting. It was pretty horrible sometimes. But I never saw any cutscenes in FFXIV 1.0 where it was that level of bad.