Here is my predition:
1. The world order doesn't change much, not much difference from now. If you think 2050 is a big deal, then go back to 1900, all those big powers at that time remain so today, a club with all old faces. My golden rule No 1: it's not easy to climb to the big power status, it's not easy to pull them down as well. Only China is an exception - Chinese weight will gain significantly but still just a new face in the club. Britain, France, Germany will still be the important powers, Japan as well. And we can't underestimate Russia, without US Russia can easily get what they lost back, the whole world won't make any noise - it's the US not the Europe that keeps Russia in check.
2. Emerging power. Honestly I look around and could't find any. India won't be a global power by 2050. The status of India today is way blown out of proportion - nobody cares India in any real hard-core world issues. If you check the main economic and technology data, India is way behind China, let alone other powers. And my golden rule No 2: Whoever fought with the biggest power(the enemy no. 1) would remain or become a world power. It's the fact since 1763(the seven year's war) and it's true for France, for US, for Germany and Japan. Russia didn't fight with the biggest power so they're less prosperous today, Chinese fought with US 50 years ago so more hopeful. Too bad for Iraq and Vietnam, they didn't attack the biggest power but were attacked. For any emergin power, you got to pass that test.
3. The war between the big powers only changes the order of the powers, but can't eliminate the other world power. If a major nuclear exchange happens then we talk about doom day, not the world order.
So basically everthing remains roughly the same, with US, China at some kind of lead. Also we got to know that today's power of the major world powers is much diluted, not as powerful as before. In relative term, US today is more powerful than Britain before the WW1, but US has much less power than Britain at that time. This trend can't be stopped, the world goes into the stage that cooperation is absolute necessary.