Just read this on CNET. We are nearing the end of support personnel in the military.
http://news.cnet.com/8301-11386_3-57618149-76/driverless-trucks-get-in-shape-for-us-army-convoy-duty/?ttag=fbwl

I am wondering...they send a whole convoy of fuel, ammo, weapons, spares, rations etc. on the road. What happens if the enemy finds the convoy and attacks it? Can it defend itself? Can the enemy take control of the vehicle and use the captured equipement for itself?

Iam sure they have thought about this, but I wonder what their solutions are

I'm not saying that combat soldiers are being replaced. But, we already have drones replacing troops on the ground.

Drones don't replace any soldiers on the ground. They fly over the soldiers to provide some eyes forward and a bird's eye view of the battlefield. Boots on the ground are still needed to control the ground. Drones, autonomous convoys, etc. will never replace actual soldiers on the ground, just augment them.

We have drones on the ground, as well.

Not really. We have small robots that are controlled by Soldiers who are close by. They are not autonomous drones like in Robocop or Terminator.

I suppose the answers are similar to manned convoys - once the enemy gets rid of the crew. (Although I don't think even Uncle Sam is anywhere near a reliable autonomous defensive weapons system yet! I expect that'll still need human involvement, even if it's "fly by X-box" from a safe bunker?...) If the gear is an add-on that still allows friendlies to take control, then it'll allow hostiles behind the wheel too.

However, I doubt these convoys would go unsupported - it'd be just as easy to add a few drones circling above for cover. And even if there are a few manned vehicles in the mix as security and breakdown assistance, turning the bulk of the convoy into drones seriously reduces the number of troops put at risk on a mission. Plus it reduces the number of troops needed for such duties, so the budget axe-men in Washington would love it!

For those pondering, boots on the ground is still the only way to securely hold an area (until the robots get truly A-I on us, as in Terminator!), but each new pilotless robot or semi-auto drone reduces the number of fragile humans in harm's way, so it is definitely the future of combat. Will we see entirely robotic infantry? Quite possibly, but given the sophistication needed to make "live or die" decisions without a public outcry we aren't going to see it anytime soon. However, attack squads of semi-auto drones with a single human guiding them could easily replace the normal human squad in our lifetime...