The Chinese can be counted as a threat to world stability only as much as Britain, France, Germany or the US can be counted as a threat to world stability. Personally I think that none of the above countries poses any significant threat. Merely possessing a military does not rise to the level of world threat (unless one is a peacenik, then the very thought of a standing military is a threat). I do not assume that they could never be a threat, but I think the likelihood at this point is exceedingly small.
China indeed can create a problem for other nations, but so can we. We created a problem for Iraq by restricting it in the manner that we do. That was a good thing, and I certainly hope to create more problems for Iraq in the very near future. However, you're not saying anything by merely assuming that they can't create a problem.