Yes I agree with TimmiT, that's the reason SEGA Networks exists as a separate entity... If all of SEGA was going mobile I don't think they would bother setting up separate groups within the company. I don't expect SEGAs console/PC output to get any smaller.... I just expect their Mobile games to release in higher quantity. I doubt one will take from the other.
While we cant know for sure I would bet there is at least A new Sonic, Yakuza, Project Diva in development. I think it wouldn't be a stretch to imagine a new Shining Force (unfortunately) is in development, and hopefully Virtua Fighter 6 and a new JRPG from the VC team.
SEGA don't release less in house games than they did 10 years ago... They just release less of them on console because Arcade games have fallen almost completely out of favour except with a niche audience.