There isn't one right now and I would go on to say that there may never be one in the same way that there is jQuery, for the simple fact that most (commercial) games are going to want to be mercilessly performant, which means using as little extra cruft as possible, and many of these libraries add unnecessary things or performance hits where it may not be desired.
That is not to say they won't be used at all. All of the above libraries are probably good for a great deal of small(er) games.
But I imagine on large projects many studios will find themselves starting with a library until they hit a performance wall, and then writing all the components they used in the library themselves in order to keep only the thin bits that they need.
If there is one that becomes popular it will almost certainly be be modular like MooTools (the second most popular JavaScript library), where it tries to be compact and lets you select only the components you want to use. I imagine you'll find a lot of games in the future that have a very small engine just for handling sound or just for handling images or a 2D isomorphic board, instead of games that have a (large) library that attempts to handle every possible kind of 2D game.
Anyway, if you simply want to find the most popular JavaScript engine then your best bet over the coming months is to use Google (page rank) to determine most popular. Searching for "2D game engines JavaScript/Canvas" will give you a pretty good idea of which is the most linked-to (popular) library at any given time.
(After all, try searching Google for "JavaScript library". You can guess the first result I bet!)
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