It looks like Persona 5 could potentially have the Japanese audio offered as DLC, if this tweet from Atlus PR manager John Hardin is anything to go.
John’s tweet (below) outlines that Altus are “looking into” whether the original Japanese audio could be offered as DLC, but has “no news” to share at this time. Note there is no mention of whether fans will have to pay for it like in Soul Sacrifice Delta.
So, once again: All we are confirming at P5 launch is English dub. I’m looking into the possibility of JPN vo as DLC, but no news there.
— John Hardin @ 2015 (@JohnLHardin) June 15, 2016
Given that the Persona series has grown considerably since the launch of the original Persona 4 back in 2008, adding dual audio could help this series get even bigger.
Persona 5 is releasing on Feburary 14, 2017 in the Americas for PlayStation 3 and PlayStation 4. There is no word on a European release.