Dengeki Online, Ys Seven will feature series hero Adol again, and will follow the story of the "Five Great Dragons of Altago." It's expected to hit Japan sometime this fall. As for Ys I & II Chronicles, not much is known about it, but it could be another remake like the recent Legacy of Ys: Books I & II for DS. That one will be out in Japan by summer.
IGN suspects that Ys Seven might be a game for Sony platforms, seeing as the title will be featured in an upcoming issue of Dengeki PlayStation magazine. Falcom did release Ys: The Ark of Nephistim on PSP and PS2 back in 2006, so it's not too much of a long shot to see the next in the series appear on either system (or both).