China did not have the power before. Who knows how it will act when it does? It's treatment of Tibet, invaded in 1948 and still occupied, is not encouraging.
It used to have this power and it turned all the countries in its neighborhood into tributary states. Which, all things considered, was not that bad, since it was overall a peaceful and stable relationship.
Hard to say how Communist China as a superpower will differ from Imperial China, though...
Hard to say how Communist China as a superpower will differ from Imperial China, though...