It will get better. Even assuming the Earth did move by some significant distance when everyone jumped, just give it some thought: it'd move right back once more! Getting everybody on the earth to jump at the same time. Suppose everyone on the planet weighed 100kg (which is an overestimate, 70kg is more prefer it, probably less). It is senseless, like a slice of infinitely perforated Swiss cheese that can also be solid cheddar.