The interview with Dave Filoni wasn't the only source of The Clone Wars Season 5 details in Star Wars Insider #134. The magazine also revealed the titles of the first seven episodes of the season. Here they are:
"A War on Two Fronts"
"The Soft War"
"An Old Friend"
"The Rise of Clovis"
"Crisis at the Heart"
The return of former Senator Rush Clovis (from Season 2's "Senate Spy") was certainly unexpected. And who exactly is that "old friend"? I guess we'll just have to wait and see.
Here's a scan of the relevant page from Insider:
The Clone Wars Season 5 is set to premiere in September 2012.