You know, I think I'm cooler with a movie than a brand new TV series.
With a movie, I think you'll get something loud, colorful, explosive, and fairly self-contained/stand-alone (running somewhere between 2 and 3 hours, chances are), as anime movies based on established anime are often aimed at a wider audience than hardcore fans of the original property itself.
Compared to a TV series sequel, I see less chance here to "screw things up", as it were. It may well just be "An action-packed adventure in the life of Akemi Homura fighting demons in 'Madoka World', with some appearances from other PMMM girls and some touching flashbacks". If so, I would suggest that SHAFT make a big bad main demon that's like Gilgamesh from Fate/Zero. Homura vs. Gates of Babylon could be a lot of fun.
Conversely, it could be a pure recap, with some finishing touches put on. I hope it's not that.
