It may be, but I wouldn't word it like that. The exec producer's been saying that he feels the show is heading toward its conclusion, and that its fourth season may be its last, not because they'll run out of network approval but because the story will be done.

"Shark jumping" is, imho, really better reserved for the more traditional model of American episodic TV, where the show just goes on and on for as long as they can get away with, until it runs out of gas and goes splat.