At a press conference today, Mr. Tsunekazu Ishihara, and Mr. Kunihiko Yuyama laid out the premise for the next Pokémon movie Pocket Monsters 2002. They also mentioned a few details on the next Pokémon game as well.
There is actually very little known about the game so far. The game is being developed for the Game Boy Advance. The Pokédex will be expanded to 350 or more creatures, and is related to the next Pokémon movie. Nintendo is looking at a Japanese release late in 2002. The rest of the information of this story is about the movie, but may tie into the game in some manner.
The movie centers on Satoshi (Ash) and Pikachu as they travel to the water capitol, "Alto Mare." The producer, Mr. Yuyama, recently traveled to Venice, Italy, where inspiration to create a water city came from. In this city, our heroes will meet Ratiosu, the elder brother Pokémon, and Ratiasu, his sister. Together, the pair protect the "drop of the heart." It is not known what this means at this time, and may not be revealed until showtime.
Following Pokémon movie tradition, the movie will be preceeded by a short animated film from Pikachu Project. The name of the short translates to Pika-Pika Starlit Sky Camp. The movie will come to the theaters in Japan on July 13th. No information on if the movie or the game will come to North America, but as RPGamers know, these things take time.
Update: Working with the image below, the complete title for the movie is Pocket Monsters 2002: Guardians of the Water Capital.