Los Angeles (TheStreet) -- If Apple (AAPL) - Get Report is getting into online television, cable-TV operators should probably be worried.

Reports that Apple (AAPL) - Get Report has sounded out TV programmers about starting its own online video service follows efforts by Sony (SNE) - Get Report, Dish (DISH) - Get Report and Time Warner's (TWX) HBO to enter the subscription-based streaming business. Netflix NFLX figured out this was the future some 10 years ago. Of course, former Apple CEO Steve Jobs was talking about an Internet-based TV service since at least 2009, but only recently has the iPhone maker seriously considered doing it.

For cable-TV operators, Apple's entrance into online video, the so-called "over-the-top" TV services, may be the most alarming sign yet that they need to change their decades-old business model.

"We may be at a proverbial tipping point," says Blair Westlake, a former chairman of Universal Television and former Microsoft (MSFT) - Get Report vice-president who oversaw licensing of movies and TV shows for its Xbox gaming console. "Little by little, consumers can start to cobble together their own viewing option."

Sports fans who could only get ESPN as part of a $75 a month cable or satellite subscription can now opt for Dish' SlingTV for $20 a month. With Netflix (NFLX) - Get Report basic streaming for another $8 a month, and the use of better made antennas for local TV stations, the cable-bundle looks less and less necessary.

And there will be more options for bargain-hunting cord-cutters in coming months. Sony intend to launch its Vue video streaming service later this spring while HBO and CBS's (CBS) - Get Report Showtime and Viacom's Nickelodeon are close behind.

It may not be long, Westlake postulates, before cable-TV operators will choose to emulate the smaller package of channels being offered online by SlingTV, which charges $20 a month for cable channels that include ESPN, TNT, TBS and others.

Some operators are already offering slimmed down packages. Comcast (CMCSA) - Get Report sells its Internet Plus Plan as well as a smaller package that includes broadcast channels, HBO and the cable operator's Streampix online movie service. Comcast also offers a streaming service to college students in some service territories, the company says.

But cable operators are "severely constrained" in what they can offer potential cable cutters by the agreements that they have with networks, studios and other content owners, says Craig Moffett of MoffettNathanson.

ESPN, for instance, charges the industry's steepest fee -- $6.55 a month for each subscriber, said Derek Baine of digital consultant SNL Kagan, and won't allow cable operators to put the sports channel on "tiers" where they can be offered to smaller numbers of subscribers to cut the cost.

That could be changing. Walt Disney (DIS) - Get Report CEO Bob Iger said during the company's Feb 3 earnings call that his company embarked on what he called a "worthwhile experiment" when it signed on with Dish's SlingTV to offer ESPN in a package for $20 a month.

"We believe that it's a worthy attempt to try to convince young people or younger people to sign up for cable when they wouldn't have signed up for it all or they might have waited," he said.

Cable and satellite operators will need to ramp up soon to take on over the top providers, predicts Tony Wible of Janney Capital Markets. Wible says both cable and satellite operators need to launch their own competing services , and might even be forced to sell their content to rival services.

"We're finally getting to the phase when fear perpetuates the risk of cord cutting," he said in an email.

The author owns shares of Disney, Comcast, and Microsoft