I suspect the tipping point will come when BBC Worldwide says, "Hey, guys, you're damaging our profitability over here." The David Yates' Variety report on the film could be a shot across the bow at Worldwide's instigation for Wales to get its fecal matter together.
Of course, if the 2012/2013 schedule is correct and Moffat's departure already a done deal the whole point is moot. As funnily enough is Moffat's indignation about the news of a film that, if it gets made at all, will be out long after he's moved on.