Here's the deal:
This really should have been given a different title. It is actually a sequel to Alice in Wonderland and Alice Through the Looking Glass. She is *supposed* to be 20 (actually, I think she's 17 or 18 in the movie, can't remember).
As for the whole "Mad Hatter is getting more attention than Alice" thing... Well, DUH. Mad Hatter is played by Johnny Depp. Alice is played by Mia... whatever-her-last-name-is. Who would YOU be hinging your publicity on?
And just because this first teaser trailer features the Mad Hatter doesn't mean we won't have future ones that feature other characters... It may be that there'll be at least four teasers--one each for the Hatter, Alice, Red Queen, and White Queen. They're playing up the whole "army" thing on Facebook, so maybe each of the main characters will get their own teaser trailer as well, to drum up "recruits". Each one already has their own teaser poster.
I just wouldn't worry. This is only the very first look we've gotten from the movie. It comes out in March; there's plenty of time for more teasers that don't focus on the Mad Hatter.
Joy