I haven’t checked up on this in a while, but it looks like the last “why isn’t the last roundup on iTunes yet” email I recieved was a day and a half ago, so the update was probably pretty recent. The Last Roundup has returned to iTunes in all it’s Derpy glory.
My personal episode still has everyone’s favorite mailmare, so everything is perfectly intact.
See this post for an update! Looks like Derpy was changed.