http://www.vg247.com/2013/07/15/professor-layton-may-return-in-a-new-game/
So, it looks like those still sore over our dear professor's farewell game Azran Legacy can pep up at the prospect of at least one more game with him in.
EDIT:
Two more sources have been credited from that article alone.
http://www.nintendolife.com/news/2013/07/level_5_wants_to_make_another_professor_layton_title