I think we expect the new SK regime will now pivot harder to US. We also know from what China been saying all this time, they want good relations with SK. Even saying kind words during winter Olympics to put out the fire of anti Chinese feelings caused by competition in the short track skating events. i thought that was quite unusual. Now China probably realize it's gonna be tough.
Even though the sino sk relationship is going to be rocky as SK goes more into US orbit, I doubt it will matter much overall to China. S Korea hard power is limited. As others said, economy is quite integrated with china's. If they really want to go against China, it will hurt them too. Their society now is also deeply divided as seen by close result. domestic issues like housing, equality, LBGT have become hot button issues. I dun think China is a main issue at all for them. There is no need I think for China to fundamentally change their approach. Continue to strengthen relations with Russia without calling it a formal alliance and secure that. The rest will fall into place