I usually would encourage a lens upgrade before a camera upgrade... but in this case, because you already have a decent lens and considering that your primary use is sports and action, a 7D would likely be a better upgrade than changing out your lens.
7D has a number of sports/action related features. Arguably the most important is high performance auto focus. It's the best "AI Servo" crop sensor camera Canon makes. Tracks movement quite well.
You need to know that the 7D is not as forgiving as your present camera. It doesn't have as much support for inexperienced shooters, is designed with more experienced shooters in mind... you have to know how to do your own settings.
For example, if you usually just turn the mode dial on your camera to the little running man icon and start shooting, you won't find that preset on the 7D at all.
7D has a 19-point AF system, with a discrete chip to control it. It's the only model other than 1D series that doesn't share AF function through a single processor that also handles images. In fact, the 7D has dual image processors, too, to support the higher frame rate (which can be nice, but isn't always necessary for sports/action). All 19 points in the 7D's AF array are dual-axis type. The center one is further enhanced with f2.8 and faster lenses. Your camera has a 9 point AF array with only the center one the dual-axis type. All the rest are single axis and less responsive in less-than-ideal conditions.
7D also is highly customizable. You can assign functions to various buttons and dials on the body. The AF system also has a number of modes and adjustments. It can be great if you know what you are doing and set it up right... or a disaster if you set it up wrong. Initially I usually recommend people use it very, very simply... perhaps the same way they used earlier, less sophisticated models... and experiment a little at a time with some of the fancier focus modes. The AF system of the 7D is another layer of complexity, on top of all the usual stuff (with the 5DIII, it's even more-so).
So a search here for all the posts asking for help with 7D... especially focusing techniques... just to be prepared if you think you want to upgrade to one.
The 7D also has a very nice, 100% viewfinder. It will be bigger and brighter than you are accustomed to with your current camera. I think the 5DIII is the only other sub-1D model with a 100% viewfinder. This does make the camera bigger and heavier, though.
In fact, you'll find the 7D a lot heavier and bulkier than your 450D. So go check one out in person in a store, to help make your decision.
FYI, the 60D has a 9-point AF system that might look like the one in your camera. However, it's also an upgrade... all 9 points are dual-axis, and because the 60D uses a newer, more powerful processor, it's AF should be more responsive than your current camera. You might want to consider 60D too. It would leave a few hundred dollars in your pocket or to use toward another lens or accesory. It's lighter and less bulky than the 7D, but uses virtually the same 18MP sensor, so there's little difference between them in image quality. While it's not a 100% viewfinder like the 7D's, the 60D has a true pentaprism, which will be a bit brighter and bigger than viewfinder on your 450D, which uses a penta-mirror (allowing it to be a little lighter, smaller.... and cheaper).
The controls of 7D and 60D also are a bit different from your current camera. They allow more direct control... two dials for shutter speed and aperture, for example. This makes them faster in use than the Rebel/xxxD. You can do the same things with your 450D, but for example usually will need to press a button and then turn a dial, a two step operation that you might have to take the camera away from your eye to do. 7D and 60D you can learn to change a lot of the more common controls while keeping your eye to the viewfinder. Another example, the 7D has a "joystick" that allows direct and fast access to moving your AF point selection around. The 60D has an 8-way switch for the same purpose, probably more similar to your current camera.
Check out both 60D and 7D in a local store and see what you think. Have fun shopping!