Depends on what the plastic wrapper was made out of. My cat loves to eat tape (I have to lock the tape in a cabinet), but when she manages to eat a piece, it passes normally. Watch for the wrapper in the stool. If the cat doesn't go to the bathroom for a couple days, take it to the vet.
It probably will pass. Like I said before, watch out for the cat's stools and make sure he's actually going to the bathroom. If he doesn't, whatever he ate could be stuck and blocking his system, so you have to take him to the vet to get unblocked.