For those not following on Twitter, a representative from Bellwether Pictures (Whedon's production company) tweeted the following this morning:
Looks like some of you might have heard that a little film, #MuchAdoTheMovie, will be premiering at #TIFF12 Sept 6-16. More details soon.TIFF is the Toronto International Film Festival. They are holding a press conference as we speak, when the full fall lineup will be announced (currently their site appears to only have summer listings).
UPDATED - More details, including a video, now available. Strangely I do not hear Whedon's name mentioned in the video but he's clearly included in the writeup (along with a hint that his movie will likely be one of the biggest hits of the festival).