I think they'll start trying to phase in robots or robitic tanks, drones, sentry guns etc. to replace grunts. Although I could also see human augmented robots... like battle mech type things.
I personally think it will be still humans, albeit enhanced or robotically/technologically assisted humans that have robots supporting them.
Like say a squad of humans with mech suits, then for their heavier weaponry, like machine guns, AT etc. they've got robots they can issue orders to.
However I think they'll still be under human control and that humans will still be used.
Like say if we still have tanks... they might be controlled by a forward command post or some such.
Main thing I think is we will still need humans to make the decisions...
One real big issue though is that robots could be controlled by the other side... like say the enemy somehow cuts communication to a robot force so there is no control... then they seize them, modify and use them against their own. I'm sure there'd be some sorts of fail safes devised but it's quite a big flaw with robots.