The last time gamers heard news about the upcoming Phoenix Wright/Professor Layton crossover was way back in 2011. Despite the long silence, Ace Attorney creator Shuu Takumi has said that the development process of the upcoming 3DS adventure game Professor Layton vs. Ace Attorney was still going fine and, in fact, was nearing its end.
According to a Famitsu interview (via Andriasang) featuring Takumi and Ace Attorney movie director Takashi Miike, Takumi said that his life is totally focused on completing the game. "The production of Professor Layton vs. Ace Attorney is at its climax. While I still cannot say much, [the game development] is progressing well, so please wait a bit more."
On a related note, both Takumi and Miike discussed the possibilities of a sequel to the Ace Attorney movie. Miike said that he would rather use film as a medium to show sides of the story that weren't present in the games, provided he has full creative reign over the possible sequel.