Let's discuss that from where, the WWIII might start?
1. South China Sea (US teaming up with it's allies in South China Sea and provoking China by attack on it's navy)?
2. Middle East ( 2 or 3 Arab countries joining for offence or defence against Israel?
3. War on Kashmir?
4. Any other place ( Probably by direct conflict b/w USA and Russia on major Cyber Attack etc)?
Not sure really but honestly, none of the four scenarios you mentioned seem likely.
- With deep vested trade ties and China rapidly growing its influence around the world, the two super powers will try to avoid any conflict that might end up challenging their "Super Power" status.
- I don't see ANY Arab country going against Israel. Not unless there are some drastic changes in these countries first. Kind of a revolution.
- Not likely. India again also is a growing economic power, they wont want to trigger anything that hamper that progress. Pakistan on other hand will remain focused on improving economy and maintaining credible deterrence.
- If it didnt happened during Cold War it wont happen now!