Judging by the great number of "clan tags" I see in use just on a cursory examination of ASE (and not counting all the people who "smurf" without their tags, heh, you guys know who you are!) I'd say clans are fairly well represented in JA so far.
Of course that says nothing about the size or skill of any of those clans, but hey, nobody said being in a clan made you a better player necessarily or that "bigger = better" with regard to clans.
As I see it some people have more fun playing with a regular group of people than by themselves. Theoretically playing together frequently would give you a good understanding of each person's strengths and weaknesses and help you play as a more solid team (which would be very helpful in tournaments and team based situations).
Plenty of JK2 clans haven't moved on to JA or have "given up" on JA, but then new clans have been formed that didn't exist in the previous game and some have been reformed/recombined/split, etc and some clans play both (and more) games, so I'd say it's probably growing and we'll see in about a year if it's more, less, or equally popular as JK2 was.
PS: I won't dig up the can of worms people are already beating again against the dead horse of the "JA sucks it takes no skillz!" people, but I would ask you this question: "If the game is so easy to master, why isn't everyone a master? Shouldn't every game end in a draw then in every gametype? Or are you contradicting yourself by saying its random, in which case nobody could ever master the game, period, and thus consistent wins would be statistically unlikely to ever happen, like in gambling?"