Not a lot, besides what history tells us:
Character: Kazuma Kiryu will be playing the role of Sakamoto Ryōma the man who sought to overthrow the government and restore rule to the Emperor. A visionary learning that the only way Japan could hope to compete with outside forces was to modernise.
He envisioned a Japan where all men were equal. Doing away with the casts of samurai and peasantry.
A Younger Kiryu?: According to records Sakamoto Ryōma died at the age of 33. He had a wife and adopted child (also a brother and 3 sisters!). Could we be seeing a proper relationship in this game along with a much younger Kazuma Kiryu? Possibly adopting Haruka?
Read more about Sakamoto Ryōma here.
Time period: Set just before the Meiji restoration era Ishin is not a direct sequel to Kenzan, which was set during the Edo period, in 1605. The Meiji restoration (Meiji Ishin) period spanned from 1868 to 1912. Specifically though this game should be set between January 3, 1836 – December 10, 1867 the birth and death of Sakamoto Ryōma.
Platform: With Ryu Ga Gotoku Kenzan! being the test for creating an engine for all subsequent Yakuza games on Playstation 3 it is possible this will be the test game for the Playstation 4 incarnation series, however, nothing at this point has been confirmed.
When will it be released?: According to today’s unveiling the game is currently in its planning phase meaning we will likely not see it released until 2014 in Japan. We will hear more about the game in the August 22nd issue of Famitsu!