Tell you what, go buy a ef 50mm f1.8 lens. They are only a $120 bucks or so and it will work on any future camera you might get. Don't worry about anything except noise. See if a better lens will do the trick for you. Use LR/PS to edit and correct the shots. You just might be pleasantly surprised.
"Don't you mean the 1DX Mk II?"
Yes I do there Robert. I had my 1D2 in my hands at the time and matter over mind won out. However, I am getting used to that as I gracefully age. WHat I don't mind doesn't matter or something like that.
"You want the best there is? Buy a 1D Mk II 1DX Mk II with the Canon EF 24-70mm f/2.8L II USM Lens."
OK that is fine if you already have the 50mil. Use it and don't worry about anything except if the better lens makes a better photo fro you noise wise. I wouldn't use it as a general lens for wrestling either but you need to learn if a better lens, which the 50 mil is, makes the noise better. That's all. The lens you said you use is not the greatest we all agree on that. So let's see if a better lens is...well... better. It won't have the best FL but we don't care about that for this test.
Shoot Raw. Do all the lens corrections in LR/PS, too. Most of the guys that answer these questions are keyboard jocks. They have never done wrestling shots or used any, or all, of the gear they recommend. I have never done wrestling photos! You need to learn what works best for yourself. Hopefully before you go out and spend a lot of money and wind up with nothing better.
Ernie has done this sucessfully for a long time so follow his advice and spend a lot of mental effort on choosing the best possible location. Like retailing (another case where location is important) there isn't a single perfect location and what you have to decide is what is the best spot for the event, your equipment capabilities, and what you most want to capture from that event.
Lens reach really factors in with high school low light shooting. If you have to severely crop an image captured in low light, the noise becomes much more obvious but more problematic to me is the loss of overall image quality and effective resolution as you take a severe crop from a camera being used at high ISO.
For example below are a couple of ISO 20,000 shots from the first game I shot with my 1DX 2 last year. The first is a quick capture that our star keeper asked me to grab for her social media account before the game and that image is the full frame, the second image is at the same ISO but cropped from about 12% of the frame from an overall post-game image. The first is fine for her social media use, if the level of cropping shown in the second was necessary for that image to "tell its story" it would be useless. It could be cleaned up and improved but it would still be the story of a sow's ear and making a silk purse. The third photo is about the same level of crop but captured at ISO 125 where detail is still well preserved. You can get away with suboptimal placement with great lighting but that is rare in most high school sports environments.
While you are deciding what or whether you need to upgrade, try choosing an optimal location for SOME of the action at an upcoming event. You won't get the overall coverage but it will give you a very good idea of what your equipment can accomplish when you are optimizing the capture in a suboptimal environment.