Season Four looks like it's going to be awesome. The panel just happened, for some reason (Seth was there due to his upcoming comedy SW series and has joined Clone Wars panels before) Seth Green answered a fan's question regarding Ahsoka Tano's death (yes this fan was under the impression she's going to be killed off) and this is how Seth answered:
Green: We went to George Lucas and Tom Root said "OK, you have Ahsoka Tano on one train, and Order 66 on another, what happens when those trains collide?" George Lucas replied, "I'm not gonna tell you."
Dave Filoni followed that up by saying he has gone through eight different endnigs for Ahsoka...
I took from this that they don't know what to do with yet and George hasn't made up his mind yet.