I agree with you on the U.S. and EU, but I disagree with you about Japan.  Japan has had a long history of kicking Chinese heads.  They'll draw their katanas, even if they don't really intend on using them.  A lot of nationalist sentiments are growing in Japan's political parties and the threat from China and the lack of strong leadership in the U.S. will likely mean that Japan will drastically increase the size of its military.

Initially it was a just a disregarded claim by China until they build enough power to back it up. Legal or not, China is going to make it hellish for those South East Asian fishermen who have been living off this bountiful water for centuries. It's not justice for the neighbors and it should not be allowed by the civilized world who declares interest in freedom of navigation ( 40% of global commercial traffics ) and favors peaceful resolution ( China claims 90% of South China Sea, 1,200 miles from their nearest coastline ). Is it not enough evidences of Chinese lawlessness? The choice is clear for a forceful response, the only language China knows.

Don't call it the South China Sea anymore. Refer to it as the South East Asia Sea instead. China will go bonkers over something as silly as that. Iran was tweaked when we referred to the Persian Gulf as the Arabian Gulf instead. It seemed to lessen their perceived influence(or claims in China's case) in the region judging from their reaction to the slight. It would be interesting to see China's reaction to the name change.

I would suggest though that the post you reference is correct -  the PRC will be highly selective in terms of the action it takes especially in regards to merchant shipping - any notable action against those whose territory it contests will (hopefully) at least focus hearts and minds in the right places but I very much doubt you'll see the sort of universal condemnation - it will be called "a territorial dispute" with the usual meaningless UN fluff (we call on both sides to exercise restraint) recently seen over the Senkaku Islands. 

There's a petition with thousands of names to change the name to South East Asia Sea, not sure if that would drive China crazy or not, but hopefully stop them from using it as a reason for owning the sea, just because the word China in it.