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Nickelodeon were suppose to air Season 5 episode 24 last Sunday but changed it to a movie, It says on Nicks website that the next episode of winx would air till the 3rd of August, I think the reason they had this episode gap was to air the season finale closer to the Season 6 trailer, which is due to air in October. But some fans got fed up with the episode gap since Season 5 finished in some countries months ago, so some fans have already watched it in Italian and alot of spoilers were posted online. So hopefully it should air tomorrow, Hope this helped!:3

I wondered too. But it may come back next fall of 2013. Sadly. Maybe after winter break.