As somebody before me said, this is in the planning phases. That means it could be a VERY long time before it comes out, and why not? You can't rush greatness. (If you do, there's a good chance of suck.)
So, two, three, four, fivesixseveneight more years? You really shouldn't expect anything right now.
I'd like to see what happens after the witches with their new enemies. Maybe as like an OVA or something not a full series. But if its like new characters with Madoka as goddess(like she became at the end) then I would like it.