War is not likely to be happen soon, because China has been surprisingly low key about this internationally. I think China is trying to solve this diplomatically, but if negotiation with India finally breaks down, expect China to start go on a PR campaign in UN and various international forums to isolate India.
I know India is treated much more favorably than China with West, but even Indian cannot spin this one to their advantage, India is clearly at fault here, no nation has the right to invade another nation on behalf of the 3rd nation.
All China has to do is by asking US: Do you find India's action acceptable? If US do not take position or take on India's side, then China just say then I guess it gives me the right to attack California, because all I need to do is to sign friendship treaty with Mexico who have border dispute with you. Also China can tell US that if you want to uphold the international post WW2 order created by you, you need to take a position on basic sovereignty issues, if not, then the world order that you helped to build is worth its paper in shit, that means we China can do whatever we want in South East and Taiwan, after all, you are not willing to reign in your own ally who is walking all over the law that you created only for the sake of countering me, that means you are also trashing your own world order, that means I can do the same etc.... Not even Trump is stupid enough to dismiss this.
Anyway, if negotiation break down, expect China to start massive troops development in Tibet and Xinjing while deploying navy into Indian ocean, then expect China to go on PR offense to isolate India, after that, war will began.
We are no where near that point yet, I think we are at best 15% progress. I do see China is saying their patience is wearing thin with India, and I'm seeing more and more Chinese media start to talk about this to wiping up support within China.