I think in years to come, after nato defeat in asia is no secret, countries like india and china will like to take their share on south asia. China would almost certainly like to stretch it arms on korea (formerly a part of china till beyond 1900) and japan (enemy of two thousand years). India would like to sharp its teeth on bangladesh, burma, malaysia etc. Given the weak militaries and strong economies of these countries its a very likely occurance in my opinion.

I don't think the Indians or Chinese would have much more luck in south east asia than the Americans have had in Afghanistan and Iraq - it would just become a quagmire for them (assuming they would actually try such an adventure, which I doubt).

Malaysia and Indonesia are different to China or India - both by ethnicity and religion and would likely resist foreign military interference pretty vigorously.

In any case, as oil production in the region is in decline, the available "prize" is far less tempting than Iraq's oil riches - where is the payoff for a military campaign ?

As for Japan and the Koreas, all are nuclear capable - the Chinese wouldn't invade for the simple reason that nuclear powers don't invade one another. And that is the end of that.