Dave Filoni has said from the start that Ahsoka is his continuation of Rebels, and that he’s been wanting to do this for over a decade. I think the delay with Season 2 relates more to the current emphasis on feature films. They feel they’ve overdone it with series and have Filoni busy with the big screen. Features do make more than a season of series when they’re successful but Lucas was always hoping to do live action TV. So Disney is split in its vision.
If they would just let KK go and give leadership to Favreau, most of their vision casting conflicts would end.