I have to say, that I'm fine with never getting jap voices added. However, IF they decided to, I think it would be nice to be able to pick and choose which you wanted in japanese and which you wanted in english. Like how MvC3 did.
For example, Kunoichi's japanese voice is horrid... And other characters have horrific english voices. Being able to pick and choose the one we wanted would be a neat way to do things.
Personally, I feel that's how most games with multiple languages should be anyhow, but that's just me.