they gotta write and refine the storyboards, animate it all, and double-triple-octuple check to make sure nothing forgeted up along the way. not to mention they have to make the songs...
then again all that could already be basically done and i'm wrong so idk
depends on how they go about in the process, which i'm unfamiliar
if i had to guess, they're probably in the animation phase for the first few episodes but still in the planning stages for later ones.
they said at ComicCon that there were no animations made yet, which is why we got storyboard animatics instead
this is a guess of a basic process lineup: script > voices > layout/storyboard > redo voices > other things like songs > animation > background music > editing > review/publish
and i believe it has been said that they usually have several of them going on at once, so you might have two at the script phase, three at second voice recording, and so on
(also, daniel ingram has stated yesterday that he has completed 79 episodes of underscore so some of that is likely pony)