Will we see a fully armored robo-grunt in our lifetimes?
Body armor already exists, but it's heavy and cumbersome. So a seriously armored suit would have to have a powered exoskeleton if a soldier is expected to wear it for very long, while moving strenuously. Especially if he had to carry loads at the same time, such as extra ammunition. (Ammo is heavy.)
They've already experimented with 'Iron Man' suits, but the complexity is daunting. There's a huge number of actuators necessary, along with problems with the delays between when the man inside moves and the suit responds. There are power supply problems and all kinds of difficulties.
Some of which are discussed here:
http://exoskeletonreport.com/2016/07/military-exoskeletons/
I expect powered exoskeletons to appear in the construction, warehouse and heavy industrial contexts before they appear on the battlefield, to enable humans to perform heavier tasks 'by hand' so to speak. In these applications they won't have to move as freely or have as much endurance. They can be connected to an external power supply.
http://www.sarcos.com/products/guardian-xo/
Some elements of this are likely to appear on the battlefield before others, such as helmet head's-up displays and data-links. Jet pilots already have that, so I expect that foot-soldiers will get it before long.
Speaking of aircraft, there's a huge amount of development work being done on what they call 'UCAVs' (unmanned combat air vehicles), basically armed remote-control or autonomous drones capable of maneuvering more violently than meat inside could withstand. The familiar Predator and Reaper 'drones' are the first wave of this development.
https://en.wikipedia.org/wiki/Unmanned_combat_aerial_vehicle
I expect unmanned ground battlefield robots to appear fairly soon. Armed combat robots probably won't be driven by AI at first, but more likely by remote human operators using some kind of virtual-reality telepresence. The practicality of that will depend on how robust the data links are. I wouldn't be surprised to learn that some of the newest tanks have an optional no-crew mode.
But I don't expect the first ground battlefield robots to be humanoid 'grunts', or men in 'Iron Man' suits. They will be armored vehicles.
If one is blown up, you won't lose a trained crew, the remote operators' VR displays will just go dark.