Sonic Adventure is coming on the Dreamcast's 11th anniversary, September 9. 9-9-10 doesn't quite have the same ring as 9-9-99, though.
The games will also have new features:
Sega of America wrote:Each game is based on the original Dreamcast incarnation, featuring all of the gameplay that older players fell in love with. The games incorporate all-new enhancements and features such as high resolution visuals and surround sound. There will also be online leader boards, allowing players to compare their skills with friends across the world! In addition to this, all-new Achievement and Trophy integration will be available for each game released.
No word on Phantasy Star Online yet. I have to wonder if they'll make downloadable content available for released DC games. I know PSO and Skies of Arcadia both had some downloadable quests in their Dreamcast incarnations.