I totally agree with Nathan here... it'll be a miracle of sorts if the show makes 100 episodes, but 400 is totally out of reach. Look at the Simpsons, they just had their 400th episode last year and that show has been airing since 1989.
Lucasfilm may have high hopes and dreams for this show but if the ratings are bad then the network will have no problem axing the thing. That's really what I'm worried about here. Star Wars shows are really only going to be watched by Star Wars fans. You're probably thinking that there are tons of Star Wars fans that will make this show a ratings success but you have to remember that there are OT purists who will not watch anything set in the PT era, there are Canon purists who disregard the EU... so really the show is only going to be watched by the hardcore fans who eat up anything Lucasfilm gives them with a spoon.
I hate to sound so negative but it's really funny how McCallum has all these false hopes and dreams for the series... they should just focus on trying to make a good show that will hook not only SW fans but casual fans as well because once the ratings go south... it's over.
EDIT: Woah, didn't notice Nathan's post was from a 3 months ago... oh well, same argument still applies.