The application pool is alot larger than it has been in the past so im not sure if they are wait-listing everyone who is not accepted as they have done in the past, that is something you may want to ask Jannette about?
Also, even though they interview they may still wait for your Jan MCAT scores... my boyfriend was planning on re-taking his MCAT in Jan as well and was told by Jannette after he interviewed that if he was wait listed he should go ahead and re-take that MCAT, luckily for him he was accepted with his current score. If you really do have a stellar application though and your interview goes well I'd say your chances are good of getting accepted, but if not, re-take the MCAT and they can review your file again after your new scores come in.
I had a friend who interviewed at another school (the interview went really well according to her) only to be rejected afterward because they said her MCAT wasn't high enough. Why they would interview her when they thought her MCAT wasn't good enough is beyond me, but it just shows that numbers do still count, even if you've made it to the interview. But... if you can knock their socks off they may be willing to look past the 20 MCAT, especially since your GPA is good!
I wish you the best of luck and if you have any questions just ask!