Assuming it's cartilage dammage, he'll have two options. One, they can trim the damaged part of the cartilage, and leave the part that can be salvaged. This is a meniscectomy, and carries a very brief recovery time. If I was a betting man, this is what I would put my money on happening. The second option would be sewing the damaged cartilage back together, and letting it heal. This would require a lengthy recovery period, including some time with it completely immobilized, and wouldn't necessarily preclude further injury when he comes back. This is also only possible if the cartilage isn't too badly damaged and can hold stitches.
This is all also assuming that his injury is just a cartilage tear and that it's on the medial side. The lateral side doesn't have the same blood supply, and a meniscectomy would probably be his only option. Either way, surgery to repair or remove damaged cartilage is way less invasive than the acl reconstructions he's already had. No matter how they proceed his surgery will be arthroscopic.
I don't want to say that meniscus injuries aren't serious. They have obvious long term effects (inevitable arthritis and probable knee replacement at some point). They're infinitely easier to recover from than ligament reconstructions though. It's not even the same ballpark. If this is just a matter of Ings having his knee scoped and trimmed, then he'll be back to training in no time. This isn't as devastating as people are making it sound. Gutted for him, but he'll be ok!