Deep history in action?
Vietnam: Rebelling against China since before Christ – turns commie (if with a marked nationalist brand, as Linh Dinh will tell you); hates China anyway, and building defense ties with the US.
Korea: Near always a loyal vassal to China – gets bifurcated thanks largely to China, becomes ferociously anti-commie (ask, for that matter, the Vietnamese – South Korean troops were more motivated, effective, and brutal than American ones during the Vietnam War), hosts 25,000 American troops on its territory, but has long maintained warm ties with China and is now apparently prepared to sidle up closer.
Food for thought*.
Anyhow, this would be a major coup for the Sinosphere.
South Korea is the world’s third most technologically complex economy, and while its future doesn’t seem that prospective (last year its TFR fell below 1.0 children per woman, and twice smaller North Korea probably had more births for the first time ever), tech transfer in the meantime could be a major boon for China.
One additional important point is that South Korea also has good relations with Russia. These should be aggressively developed, as it is perhaps the only quality country that is quite Russophile. Better relations with South Korea will help undercut Western sanctions, while avoiding too lopsided a reliance on China for that function – while not coming at the expense of relations with China, since it has good (and improving) relations with Korea too. In contrast, Japan is too hostile to Russia, while Vietnam and India don’t really have anything interesting to offer – and have bad relations with China, besides.
* This would also further confirm that theory that formal ideological alignments play a much lesser role in East Asia than they do amongst Europeans.