In last night's Panel Borders radio show, Howard Overman confirmed he's writing a Misifts movie.

Here're the timecodes for the podcast:
4.19: Whether or not you've completely seen the end of Simon and Alisha if our movie has its way is another issue...

28.55: I've written the first draft of the script and we'll see what happens.

You mentioned the possibility of returning characters... is it going to be set in the past of the show or...?

I'm not going to give that away! If it happens it will involve past and present characters, I'm not allowed to give away anything more than that.

The website for the podcast of last night's episode is link and it'll turn up on iTunes in the next 24hrs link