UPDATE: Siloconera picked up that the PR manager for Atlus USA (And Sega of America, for that matter), John Hardin posted earlier today that he is looking into the possibility of getting Japanese voice overs into Persona 5 in the form of paid DLC. He described it, however, as "a massively steep, uphill request."
During E3, Atlus hosted a Japanese stream revealing more information about the upcoming Persona 5, along with a gameplay reel. The front and center of this stream was the revealing of a ninth party member, Goro Akechi, a high school student and detective. Beyond that, not much else was revealed about this character, and the gameplay shown was identical to what has already been shown via an IGN recording.
After the stream, Atlus released a number of trailers going over "cooperation characters". The batch of trailers focused on the characters of Tae Takemi, Muneshisa Iwai, and Sojiro Sakura. These cooperation characters can be met either in school or in the city, and upon forming bonds of mutual trust, you will form a "Co-op" relationship with them, and they will assist you using a special ability unique to each one of them.
The Japanese site for Persona 5 also opened up the pages for "School Life" and "Phantom Life" (the second and third top links on the site, respectively). Also announced was a Persona 5 themed premium event at the Tokyo National Museum. The event will take place on July 19th, and will also have live stream coverage on Niconico.
Now for a bit of news that will very likely come with many groans of exasperation and annoyance: Siliconera picked up that Atlus announced that the English version of the game will feature no dual audio option. The only option for English copies will be the English voice and text, with no Japanese audio. Atlus' statement on the matter is that their localization team "offers an English script that provides a faithful and engaging play experience." At E3, there was a sample of Morgana's English voice, which may likely have been provided by Cassandra Lee Morris, if a teaser tweet on her profile is anything to go by.
Persona 5 will be coming to PlayStation 3 and PlayStation 4 in Japan on September 15th, while the West will receive it on February 14th, 2017 - Valentines Day, for those that need to give a significant other gift ideas.
Update: The following additions were made: Added in mentions of a gameplay reel in the Japanese stream that were lost during a draft revision snafu. Corrected the source of the no dual audio news to Siliconera; it was originally erroneously credited to Dualshockers.