WC is still a couple months away. All it takes is another slump from SKT or another team picking up the pace to put SKT in jeopardy. They've lost enough games now that there's enough information to figure out what makes SKT lose, and more than enough information to see what makes them win. A team has already called ahead of time that they had a plan for SKT and won a series against them (KT Arrows if I remember correctly), so there is certainly a possibility of them being beaten when it matters.
Still, they certainly have shown up strong in Allstars. I'm thinking China needs to adapt their play to a different meta when they play Korea, there's an underlying pattern that Royal Club and OMG followed in their losses to SKT that hints at an unfavorable meta matchup. C9 needs a little more international experience, but they're certainly adapting well, so they might be ready for Worlds. Fnatic needs to get consistent, they're terrifying on point, but they can just as quickly become deflated. I feel it's in part to their team's strategy, as their emphasis on star players is starting to fall apart in the face of weaker players with better teamplay, so they seem to fall flat on their faces when they win lane but just can't capitalize on it.
And who knows, maybe North Korea will be the hard counter to SKT. Let's wait until WC is here before we start betting life savings.