Is it a safe bet that they would go with the same RCWS 50 cal set up that is found on the Namer, and while bringing this up, what is the chances of seeing a Auto cannon on a future Namer.There was a lot of debate over this with IDF Tankists when Mantank proposed the new loader configuration for the Merkava Mk 4 . But what the Israelis did is changed the roles of all the vehicle crew. The commander was relieved of the role of providing driving direction (and anyone familiar with tanks knows how much the driver relays on situational awareness from the commander) thanks to the rear camera and the loader being given many of these roles. The loader also has a multi-function work station that enables him to see through the hunter killer sights and other sensors. The Israelis have also been wanting to fit the Merkava Mk 4 with a RCWS that the loader would have primary operation.
As for being deficient of a crew served weapon the only tanks in the world that I know of with two roof mounted 7.62mm MGs are Israeli. So in a comparative sense with other tanks (CR2, Leopard 2) what is the shortcoming. Also the firing arc and training of the Merkava Mk 4 commander's MG was significantly improved over the Mk 1/2/3 flex mounts.
As far as having only one crew served weapons platform I really do not see a issue with this, after the bullets start whizzing by all crewmembers are in defilate mode any ways, especially the loader who needs to be quick to reload the maingun after the battle carry round has been launched.