I'm also hoping against hope for another season but all the current marketing treats this like it's the end. And they butted up RIGHT into Revenge of the Sith, so technically the Clone Wars are over. Plus they're probaably refocusing energy moving forward on new projects... *sigh*
This last season was very enjoyable, and Ahsoka has GOT to have earned a place as one of the TOP Jedi of her era after dealing with Maul, but I still want more!
It doesn't help that due to the place in the timeline it's in, it ends with a dark, downward trend. I really would've enjoyed if they never quite got to RotS and ended The Clone Wars on a fun jingoistic upswell. Something like "Wow, can't believe we went through such a great adventure/battle/intrigue. Oh no, Coruscant's under seige? Well, see ya! Who knows how this will turn out? *wink*"