i dont think walking bots will ever become a "main military weapon" in any sense, itll become a niche but useful weapons system in specific scenarios. a man sized, bipedal robot has a clear (if not quite achieved/realized yet) mobility advantage compared to pretty much every other autonomous/robotic equipment (drones can ALMOST do this, kinda): doorways and stairways. so to me, their usefulness is "attacking/assaulting/capturing buildings and infrastructure you DONT want to destroy". anything with a doorway or staircase thats too dangerous to send people inside, from a military perspective you...you blow it the fuck up. no robot will ever, ever be cheaper or more effective that just a good old fucking bomb when it comes to "remove building with enemy inside".
but say its an armory, a factory, a railway, whatever. you want to take it, but NOT destroy the fuckshit out of it? well, you get as close as you can with fleshwalkers, then deploy the walking autobots and vr headset/control directly like a fpv drone. this lets you safely* navigate assaulting buildings and infrastructure, and more importantly, the most dangerous chokepoints of said buildings, the stairs, doors and doorways. once your clankers cleared the dangerous stairway, doorway, or door, and clears the floor, your fleshwalkers move in and rinse and repeat each level.
outside of that, itll be niche as fuck for the military. swat, law enforcement, firefighters will definitely fuck around with this for the same reason, stairways and doors. they have a lot more incentive to save buildings and not go silly willy with explosives on everything.

dont get me wrong, i sure with we would get IRL crazy terminators dual wielding something like that microgun, the 5.56 minigun with like 8 inch barrels, but i just dont really see it having any real use.
and yes a working, portable handheld 5.56 minigun does actually exist. its totally useless. but it sure looks cool. xm556, by empty shell. basically vaporware, but real.