CS/ECE here: the likelihood of a large robot/any robot being hacked is null to zero. The signal can be blocked but thats pretty much it. On the other hand, computing power needs to improve by 2-3 orders of magnitude to make autonomous robots feasible on a battlefield.

Current research is overwhelmingly oriented towards large clusters of small robots: they require less maintenance, have longer ranges than equivalent-mass single platforms, and it is very unlikely materials will improve to the point that a large robot/machine is feasible energy-wise or strength-wise any time soon.

Also jamming a drone would require a massive airborne jammer which could still keep up with the drone; its a lot easier to jam things on the ground (though still very hard)

Large mechs are never going to happen at this point unless hobbyists make them. The closest thing I can see happening is this: if we can develop extremely powerful railguns but not miniaturized power supplies, and still have reasons to need snipers in mountainous ranges/hazardous territory, we may need a legged power supply (think big dog) to power the railgun. Railgun (or any electronic, long range weapon) technology is very unlikely to be miniaturized to this extent though.

Another thing I could see happening is if we started using biomechanical robots. Muscle has an extremely high power density, and relatively low density fuel requirements (though ATP in solution would be very expensive to create). Something like a mountain goat crossed with an elephant, with metal bones and composite skin would certainly have a place in the army to replace trucks in rough terrain. Napoleon crosses the alps all over again... Anyway, hats me speaking out my ass.