That's what the last line is for. We still need troops to hold an area. Which, as you said, includes fighting. Though honestly this would be a hugely onesided battle if you don't want to destroy the area - enemy gets to use bombers, turrets, and missiles, you get soldiers.
Anyway, we're talking future. In the future, I'd say costs would be less of a concern (just with the more commonality). I don't care if drones are expensive, if they can replace infantry for targeting then that's fine.
Drones are also vulnerable to enemy aircraft, AA, jamming and hacking.
And infantry are vulnerable to enemy sentry's, automatic fire, enemy infantry, and heavy support. Difference? A dead drone isn't a dead human.
My point there was that drones have fundamental weaknesses that must be covered with ground forces. You can't just say "well infantry can be shot" and everyone will go "oh I guess we don't need them then."
You're also still comparing infantry against a combined force, when any war between major nations is a combined force against a combined force.
Do not consider drone strikes against Pakistani militants and/or children a good example of the usage of drones in a shooting war.
It's all very well saying you don't care about the cost, but it is something that must be considered. As drones get more advanced, their cost also rises, as does the cost of their weaponry. The
average cost of a hellfire missile is $99,600. A nation can only afford so many munitions. If that hundred thousand dollar missile has to be used against one of your infantryman rather than your own drone (note that hellfire missiles are AtG, it's a metaphor) then you have lost a significantly smaller proportion of your forces.
What do you mean by 'turrets' and 'sentries'? You do realise this isn't team fortress 2, right?
I... also cannot comprehend the implication that infantry are obsolete for the most part because they are vulnerable to infantry. If you want to fight infantry with infantry, by base logic you need infantry. If you are fighting their ground forces with your own, you are not just using them for occupation.
Both drones and airstrikes were used in the Gulf War; ships utilised both missile strikes and gun bombardments. It was all the modern weapons of the era deployed. By this logic, there wouldn't be much use for ground troops, right? Well, no. Armoured and ground divisions were still the deciding factor. They didn't just occupy territory - they took it. The wars in the middle east, such as the Syrian conflict, continue despite airstrikes - the bulk of the fighting is done by ground forces. Both are modern examples of war.
Future development of more reliable ways of AA - such as lasers - will only increase the need for effective ground forces over airborne force projection.