The newest Star Wars Insider magazine is supposed to come out the day before Season 4 premiers (where I live, anyway) but you can take a look at some of it's content HERE. (Warning, spoilers)
So Jar Jar is going to fight General Grievous. I have got nothing against Jar Jar, in fact, I like him a lot, but this is taking it a little far.
By some of the pictures in the magazine, I think that they brought Padme along so she could negotiate with the CIS. Nothing like aggressive negotiations, eh? ;)
The animation is going to be so much better in this season. Dave Filoni said that in one battle in Season 4, they had to remove 5,000 characters from the screen, and there was still thousands of characters in that episode! Plus, Rex is going to have his own arc!