The leading providers of streaming-video content are churning out more original programming, setting the stage for an eventual showdown between traditional broadcasters and over-the-top upstarts such as Hulu, Netflix and YouTube, observers say. All three companies are preparing to debut original programs in the coming months, and their success in enticing television stars to join their casts is a sign the medium is gaining traction, executives say. "The time is right. We're finally here," says Yahoo!'s Erin McPherson.