While it's interesting enough that an adventure game expert from Level-5 and Chunsoft would be working on an Ace Attorney game, there are two more parts of that tweet that we want to press. Ishii obscured the last half of the title, suggesting that it's not Ace Attorney Investigations 2, but rather something unannounced, with a new title. Furthermore, he said he's working with "Takumi-san," likely series creator Shu Takumi, who hasn't been directly involved with the games since Apollo Justice. Which also suggests it's a new game. We'll be in our office reviewing the case files until more evidence comes to light.