World of the future?

[Kagemusha]

What do you think,how the situation in global scale will develop during the next 50 years? To me it seems that China and USA are the only real contenders currently of the leading country in the world. There are other serious players,like EU,Japan,India and Russia, but i dont think any of them will be able to challence US as the leading power on the global scale, not that i would even wish that either.
There has been lot of talk about China lately and it seems some are ready to create a boogey man, like good ole Soviet Union out of it. Some think that China is trying to turn into a military superpower like US and some even think that there will be war between US and China in the future.
My question is why China would like to go to war with US or even try to challenge US as military power? With its economical growth and potential, could it be possible that in matter of fact China is just bluffing. Playing its politics pretty much like US did to Soviet Union during the Cold war. While US constantly increases its defence spending,which is already over half of its federal budget. Here is a pie chart of the US federal budget for 2008:



There arent much to know about Chinese budget figures, but it seems that while China has large army, the spending is not that heavy,when one looks at the equipment of the soldiers,their navy and airforce. Infact the army doesnt look like that it is in state to start any major conflicts, nor end those succesfully.Could it be possible that Chinas simple plan against US is to simply outgrow US economically and can that be achieved by China with its three times bigger GDP growth?