If you have been paying attention on the iCarly Wiki lately, you'll see that there is confusion on the amount of episodes in the 4xx production season. At first, it was believed to be 13 episodes long, but new information is contridicting that. My belief is... iToe Fat Cakes marked the end of season 5 (4 production). Here is some proof:
DanWarp's Twitter Post stating at least 24 more episodes would be made, maybe more!
(Proof: Production Season 3xx and 4xx equal 24 episodes if 4xx is only 11 episodes.)
Production Season 4: Filmed May 2 - July 22, 2011.
(Proof: Only 12 weeks of filming and a week spent traveling to Memphis during May. iBalls clip was last video shown on Dan's YouTube before production stopped.)
Miranda had to continue her Sparks Fly/Dancing Crazy Tour.
(Proof: Miranda was in very little of iBalls (410), iToe Fat Cakes (409), and iBloop 2 - Electric Bloopaloo (411))
It would make sense that Dan could only squeeze in 11 episodes.