Sony does not need Call of Duty. They can focus on reviving Syphon Filter. If Microsoft is willing to sell off IPs/studios that are not doing good, Sony can buy Halo, Perfect Dark and InXile. Halo needs to get out of Microsoft.
Maybe they can make a new studio with old devs like Jason Jones, Joseph Staten, Michael Salvatori, Lars Bakken, Tyson Green, Chris Butcher, Ben Wallace and Marcus Lehto. Maybe even call this new studio Bungie.