No, there will not be many more Dreamcast releases, but the Dreamcast releases they are putting out I would not be surprised if they are ported to all active systems
Sammy is currently planning a more expensive, and therefore more powerful, arcade board in the near future and, as powerful as the past Sega boards have been, I would not be surprised if they ask or request "help" on their next one, and Sega could in turn develop for more powerful hardware. It would be a bad buisness decision for Sammy to force Sega out of Triforce or Chihiro development though, as they have not made back their efforts yet.