How would you occupy a city with only drones? What would it look like? Would they issue orders to civilians to stay in their homes? What sort of objectives that humans do now in war [0] do you think drones can fully replace?
[0] establishing forward bases for further logistical support, "securing" areas, including searching through rubble for humans and making sure they're not a threat, etc. I've never been in the military so I don't know from experience but I'm pretty sure there's tons of other examples here.
There are some experiments using turret style drones to maintain like DMZs. They still need a human operator. That is a case where you are mostly just waiting though.
Seizing a town means dealing with a ton of civilians - negotiating, handling mixed reports, etc. Drones may become part of that but cameras are imperfect and you will need people unless Drone tech has a giant leap in human interfacing.
Half-life 2 confirmed.
Infantry and AFVs that support them will never go away. They may change but war isn't just about destruction.