I have little doubt that every effort will be made to clear this officer. He will say he was in fear for his life and will provide evidence to support that (scuffle in the car, Brown advancing on him). The prosecution (if there is one) will say he should have waited for back-up, should not have chased Brown. But, in most of these cases, the cop is given the benefit of the doubt unless there is something obvious about the cop's behavior.
In practical matters, Wilson will never be able to work in Ferguson again. He will either resign or be fired and that may, in itself, resolve the matter.