I was at Disney last week and we were told by several cast members that it was coming. Then I saw this on WDW Magic so you know it is happening. I have an old Fastpass so I took a pic here it is:

Fastpass from Disneys Big Thunder Mountain Attraction

old fastpass

The time on it is 1pm to 2pm you could come back anytime between 1pm and 2pm and ride the attraction but Disney was not enforcing this and you could come back anytime after 1pm and ride even if it was after 2om. This will be changing starting March 7 2012 and Disney will be enforcing the return times, there will be a window of 5 to 15 min around the time on your fastpass but anything after that and you will not be allowed to ride the attraction. So make sure you adjust your plans because many of us grab a fastpass and just go back to the attraction after the opening return time. Not anymore!