Mercedes and AMG have yet to confirm if the M177 will get Camtronic. Mercedes did confirm that the M177 will be a 4.0 liter V8 and it will be based on the M270/M274 four-cylinder architecture. With BMW set to give the new M3/M4 S55B30 motor Valvetronic Mercedes will likely respond with Camtronic in the C63 V8 so as not to appear behind in engine technology or efficiency.
So what does Camtronic do? At partial load the system switches to a low lift cam profile limiting airflow which allows the throttle body to stay open and limit pumping losses which improves fuel economy. BMW's system is similar but completely variable whereas the Mercedes system is a 2-stage design. The argument from Mercedes is their system is cheaper as it involves fewer parts while being 80% as efficient. What it all essentially boils down to is 4% savings in fuel economy. BMW's system being continuously variable does bring the benefit of the throttle body essentially being eliminated as it is always open (except at idle) although it is retained as a fail-safe. The M177/M178 will retain a throttle body as the M270/M274 do.
How does Mercedes accomplish these airflow changes? There is a hydraulic camshaft adjuster that can adjust through various ranges. The intake camshaft has two movable pieces which are hollow. There are two profiles essentially for higher lift and lower lift. When the motor needs to switch, the actuator will apply pressure to grooves in the cams and within one revolution of the camshaft the necessary profile is engaged.
The easiest way to break this down would be akin to having a fast and slow cam all in one. Whether the C63 will get this technology or not remains to be seen but with the emphasis all OEM's are putting on fuel economy and the fact the architecture the motor will be based on already incorporates Camtronic the odds are in favor of it. Will it complicate tuning? That remains to be seen but it certainly won't make it easier.