Hey there! I just found out that there is going to be three more new pokemon mystery dungeon games! Here is the source:
It should be somewhere on that page... these games are to be called Pokemon Mystery Dungeon: Keep Going! Blazing Adventure Squad!, Pokemon Mystery Dungeon: Let's Go! Stormy Adventure Squad and Pokemon Mystery Dungeon: Go For It! Light Adventure Squad! No (proper) information (e.g. screenshots, etc.) has been given apart from a scan from a Japanese forum which can be seen on the link I posted.
Feel free to discuss about these games whether they're going to be good or bad, whether you'll buy it or not, etc.