It should be stated, so it's clear, that the Horde and the Alliance are both working together here against the Kor'kron. Without wishing to be too spoiler-y, it relates to the warm-up for the raid we know is coming at the end of the expansion, this is the beginning of what will likely be a fair ramp-up of wrongdoing from Garrosh.
Anyhow, these caravans. They are quite the exciting new feature, along the lines of a very basic dynamic event, like those in Guild Wars 2. How it goes down is that an indicator will appear on the map, along with a zone-wide announcement, saying something along the lines of "A supply caravan needs to be escorted from Crossroads to Far Watch Point". You then need to head to where that caravan is, it'll be on the map as you see to the right, and keep it safe from marauding Kor'kron. These are level 90 mobs, so caution would definitely be advised for any lower level players who come across them.
Safely escorting the caravan to its destination awards Surplus Supplies, which contains items such as Kor'kron Meat, Kor'kron Oil, Kor'kron Stone, and Kor'kron Lumber. It's unclear right now whether players actually have to have killed Kor'kron mobs which were attacking the caravan, hit the mobs, or just have to be in the area, but all the same-faction people I chatted to were getting the supply boxes.
Why am I excited about these caravans? Sure, they're neat new-ish technology from Blizzard, they're dynamic, they move, but they're just an escort quest. I'm excited because they lead to world PvP. I tried this first on a PvP server, where world PvP is pretty par for the course, and then on a PvE server, where it isn't, and in both cases this led to big battles between the Horde and Alliance. I could have just been lucky, and I'm not exactly sure what led to it, whether the mobs were flagging people, whether it was flagged folk messing things up on the PvE server, or what, but it sure was fun. And when there wasn't PvP, people from the server were just coming together, chatting as they walked. It was a really fun experience!
On the topic of caravans, there are also Overturned Kor'kron caravans, indicated on the map by the blue-gray symbol in the map shot above, in the center. Wowhead postulated
that they were a way to disrupt the Kor'kron, but it is very unclear at the moment. They don't seem to do anything but sit there!