User blog comment:Dragonknight86/Phineas and Ferb on Hiatus after Season 4 ends/@comment-188360-20140215204322/@comment-5443633-20140215220053

Basically it means that Disney has not ordered any new episodes and still holds the rights to produce the show. They will probably evaluate the ratings and marketability of the characters before deciding if it will be profitable to continue producing new episodes.