Apple has quitely removed TV Rentals from iTunes thereby you would not be able to watch TV shows from iTunes rather Apple has even removed the traces of Rentals. Apple introduced TV Rentals last year which allowed users to watch TV Shows for a small rental fees. Now as the TV Rental service has been pulled off but still you can only download individual shows or already purchased season passes.
Apple has confirmed the change recently with All Things Digital,
“iTunes customers have shown they overwhelmingly prefer buying TV shows,” Apple spokesman Tom Neumayr said. “iTunes in the Cloud lets customers download and watch their past TV purchases from their iOS devices, Apple TV, Mac or PC allowing them to enjoy their programming whenever and however they choose.”
Moreover, it has been reported that neither the Hollywood Studios are interested in Rentals as,
After carefully considering the results of the rental trial, it became clear that content ownership is a more attractive long-term value proposition both for iTunes customers and for our business. To further enhance the value of ownership, we are working with Apple to make content available within their new cloud-based service.
May be this step has something to do with video steaming service Netflix that Apple has recently shown interest in acquiring. Although time based video downloading was never appreciated but still the service rendered quite entertainment for some of the popular TV shows.