It is a definite possibility, especially when you look at the symbol. Look here:
When Samurai Goro was confirmed as an AT, his update was given under the F-Zero symbol. No big deal, right? He's from F-Zero, so he should have an appropriate symbol. That's very true, until you look at this:
When Dr. Wright was announced, it was under that Smash Bros symbol. Not one for SimCity. Since Dr. Wright is the only character in SimCity, it's pretty safe to say another character from that game won't make it in as playable. So what does that tell us? It tells us that Sakurai and his team are not creating symbols for franchises that are not getting playable characters. Only symbols that are going to be used in-game for character icons and victory screens exist. Now looky here:
An Animal Crossing Symbol, right?
This definitely bodes well for an AC character to end up as playable. Very, very well. But since all of the major characters are shown in the BG of the new shots, I can't imagine who it would be.
Edit: Ferro beat me to it, huh? Stupid dial-up internet. >_>