I'm not a continuum employee, but I believe that anaconda is updated much less frequently than the individual packages. Presumably it's because anaconda has everything so it wouldn't be a good idea to update it every time a package is updated -- if you just care about pandas you don't want a problem because of an issue with some other recently updated package that you aren't even using. I'm also guessing the anaconda distribution might have a bias towards stable and/or older releases vs development and/or brand new releases of packages.
I believe the latest anaconda file is timestamped from Nov or Oct of 2014 and there are several updates to pandas since then. Anyway, I think nothing is wrong and you're doing it exactly right. Just type "conda update pandas" if you want the latest pandas. This way also gives you the freedom to specifically choose between, say, 15.0 vs 15.1 vs 15.2 which might be useful if you hit some specific pandas bug.