In a livestream for the upcoming Etrian Odyssey Untold II, Atlus announced today not one but two more upcoming games for its Etrian Odyssey series. The first is Etrian Odyssey V, the fifth entry in the main series. No release date has been announced, but there is a teaser site here. Interestingly, the trailer and site don't mention the planned release platform, though the previous titles were released on the Nintendo 3DS.
The second announced game is a collaboration project with Spike Chunsoft. It will be a crossover between Etrian Odyssey and Mystery Dungeon, combining the mechanics from the Mystery Dungeon series with the look and feel from Etrian Odyssey. The current title for the game is "Mystery Dungeon and the World Tree", and it is planned for a release for the Nintendo 3DS on March 5, 2015 in Japan.
Currently, neither game has been confirmed for release outside of Japan. Persona Q: Shadow of the Labyrinth, another crossover between Etrian Odyssey and the Persona series, releases in North America tomorrow, and this Friday in Europe.
Official Blog post (in Japanese)