I also really hope that Phoenix becoming the main character again doesn't result in other characters from his games coming back.
Don't get me wrong. I love Maya, Edgeworth, Franziska and Gumshoe, but the latter 3 already got plenty of exposure in Investigations and Maya is set to appear in Layton vs. Gyakuten anyway. The same goes to recurring characters like Larry, Pearl and Oldbag. If they want to reuse characters, then reuse the ones from AA4 or even Investigations.
And for the love of God, don't abandon Apollo, Trucy and Ema. Klavier can go die in a fire, though.