Interesting scenarios. Lets look at them one at a time.
1. China against the US - A war of ideology and Economic influences. Principal theaters of conflict would be the Pacific, South East Asia and Eastern Russia/Manchuria.
Likely, but not a full fledged war. Both countries are economic powerhouses. Neither wants their economies to suffer because of a war. Though a small scale conflict/skirmish in the Pacific in the far future cannot be ruled out.
2. China allied with the Islamic World against the West - similar to scenario #1 but with more parties involved.
No way. China is more interested in the resources of countries which happen to have a Muslim majority. Hence they are friendly towards those countries. The market for Chinese goods are the Western countries. Muslim majority countries simply cannot compete with western countries to provide the Chinese with such lucrative markets. And China is not foolish to go to war with the west for the sake of 'Islamic World'.
3. US against Russia - The original Third World as envisioned by Cold Warriors. Less likely to happen than in the time before the 1990s (collapse of Communism) but nevertheless it is still a possibility. Would be apocalyptic as both countries still possess the largest nuclear arsenals on the globe.
If that would have had to happen, it would have happened in 1962 (Cuban crisis). The flash point has passed, never to be revisited again. Both countries are military behemoths and take their roles in world affairs very seriously. Both consider themselves responsible powers, and so do the majority of nations. US and Russia have been working closely to help solve many conflicts around the world. So a big NO.
4. West and India against China and Russia - China and Russia fighting to avoid encirclement by their enemies. Could occur if Totalitarianism is resurrected in Russia.
Very unlikely for reasons mentioned above. India too is a rising economic powerhouse and a military power. A vibrant democracy, the worlds largest, would not want to shoot itself in the foot by going to war with its ally Russia and its biggest trading partner, China.
5. US and China against India and Russia - Would be a possibility if Russia reasserted itself and realigned with India, Another Cold War Scenario come to life.
6. The Americas against Asia - A late 21st century war possibility that could occur as both continents strive for domination of the mining rights to the Planet's largest Ocean.
Again unlikely scenarios for reasons mentioned above.
7. War of the Corporations - A war situation in a post-nation state world where corporations battle one another for control of the planet's resources. This war could quite likely move into the region of space near Earth.
Interesting scenario, reminiscent of the East India Company adventures in the subcontinent. A very likely scenario, but then unlike the old days, governments have tighter control over corporations and their activities. Corporations would not be allowed to grow larger than governments. Would the corporations drive their govts to war? Maybe, but with globalization that too is highly unlikely. Though there would be intense competitions for markets.
8. The War of the Next ideology - A war in which the next counter-capitalism ideology raises its head, spreads out across the border and challenges the existing capitalist infrastructure. Counter-capitalism culture could take the form of rejuvenated Marxism or a totally new ideology (perhaps New Age) that has yet to be synthesized.
Those are basically political ideologies. Communism has failed miserably. Today's communist countries are just communist in name but capitalist in spirit. Political ideologies have come and gone, but the concept of democracy in its various forms has survived the test of time and so shall nurture itself in the future.
9. The Oil Wars - Decreasing energy resources may force the West to take matters into their own hands and force OPEC to hand over its assets.
Everyone knows that we have limited sources of oil. No one in their right minds is sitting idle for these resources to vanish and start looking for alternatives. Technologically advanced countries have been investing huge amounts in alternative sources and the day is not far when dependence on oil would be a thing of the past! So no oil wars leading to WWIII.
10. USA against Islamic world (China and India:neutral)- A situation where USA attack on Islamic world and China and India are neutral.
That is a ridiculous notion, to say the least. Contrary to many ill-informed people, US is not against Islamic countries. A little introspection would help people who fantasize and pray for such scenarios to see what reality really is.
