See, in the manga, after using Mugetsu, Ichigo loses his powers only a little while after beating Aizen with it, which leads to the rather touching scene where Rukia fades away. We don't have that, in the anime, not yet, because Ichigo will lose his powers later (In a random period of time) Urahara states that it could be in a day, in two days or in a year, for all he knows. That's obviously an attempt to make the upcomng filler "in-cannon" to the rest of the series, much like the Bount Arc is supposed to fit in the time-line (Although I'd rather have something that doesn't fit in the timeline but doesn't suck)