That's the point...
That's why you can't compare Cars to 7 months of sales and you can't compare Star Wars to 7 months of sales.
150+ million isn't chump change is the point basically.
It is chump change when a film makes a billion bucks.
10%ish of gross as merch sales is...pathetic, for a "big franchise" (which I refuse to call this film, it's not a franchise yet). And likely, that money includes video game sales at $50/whack. Most of the films in this category make many times more on merchandise than they do on the films themselves.
People say Star Wars isn't a valid comparison...it sure is, as Disney could have also announced LucasLand. A proven franchise, EXTREMELY proven marketing (they pretty much invented modern movie merchandising), yet they pick this single movie with two sequels years away that for all we know could turn out like the Matrix (as in, fizzle). And, if you divide Star Wars merchandising over those 30 years (even though in some years it was far less than others), you still have a lot more than Avatar.
There is almost no Avatar merchandise out there. Because...people don't care. There is no break-out character, there is no knowledge of the universe outside those who saw the film, and the audience is narrow. That narrow audience sure went to go see it at it's double ticket prices repeatedly, and you can't take away the $$$ thing from Avatar, but it had almost NO cultural impact whatsoever. Yay, generic environmentalist message - yeah, a blue guy already did that, name is Captain Planet.
So the same teenage/early 20's guys that drove the box office because they were so jazzed up about the 3D, bought a bunch of video games too. 153m ancillary when your film makes over a billion is the opposite of what happens with a truly successful franchise with cultural impact.
All that said, I hope they are wonderful attractions - but in five years when these new films come out, and people are either tired of, or used to, 3D, it's hard to believe that they will be anywhere near as successful as Disney is banking on with this move. I've never once heard, "Wow, the acting in Avatar was amazing!" (Though Cameron had the nerve to try to get animated characters Oscars, ROFL, he actually tried to get them in nomination!) I've also never heard, "It was so well written," or "the characters were so compelling!" All you hear is, "WOW PRETTY!"
Which, as I said above, is great, and could be good as theme park attractions really aren't that deep; *but*...there is still virtually no cultural impact from this film, aside from it's revenues. It didn't sell more tickets than any other film (far from it), it just hit at the right time with the right technology and the right (lack of) competition for the right audience. It was a grand move. But will anyone care about Avatar in 15, 20 years? I just don't see it as likely, when I can't walk around my office without seeing Twilight, Harry Potter, Star Wars, etc. calendars and such everywhere - those are franchises. So far, Avatar is just one movie that made a boat load of money from a specific audience. And not the audience who generally goes to WDW, or at least that plans the trips.
I'm hoping for the best, but I think Disney is going to be just a little too late for anyone to give a dang about Avatar in half a decade from now. This is so "blue sky" still, as was said - and the announcement was simply for Wall Street, and of course to subject us to the next five years of talking about the dang thing...cruel!