To be honest I wouldn't be surprised. Mozilla is king of not delivering on time (though Facebook seems to be rivaling them in recent years)
But for now, they've been good about moving it from Nightly to Beta, though it was in UX for a really long time (started as a test build in Jul 2012, I think it graduated to the UX build in Nov of 2012, moved to Nightly in Nov 2013)