6 speed is a must, can't see it coming with a 5 speed, 6 speed will just make it a better vehicle.
Depending on how long Chevrolet decides to keep the SS sedan alive in production, we might just see the Corvette seven-speed in the sedan.Holden stopped using the 5 speed manual when the LS1 was introduced way back at the back end of the 90's. So that is pretty safe it will be a 6 speed. I would be extremely surprised if it isn't offered with a manual so I would be quietly confident it will be one of your options (a long shot but it may get the 7 speed that debuted for the Corvette, highly unlikely but that would be good) along with sunroof and a small list of things like interior and exterior color options.
It will be highly likely to launch with the current 6 speed auto with revised calibrations and mapping.