'High School Musical 4' news: Latest installment to feature all-new cast but Zac Efron and Vanessa Hudgens rumored to do cameos?

Casting for "High School Musical 4" has begun, and while no confirmation has been given yet, fans are hoping they would get to see some of the original cast members, particularly Zac Efron and Vanessa Hudgens, do cameos in the latest installment.

Gary Marsh, president of Disney Channel Worldwide, has already announced that the upcoming movie will showcase an entirely new cast. However, a throwback photo posted on Efron's Instagram account has created a buzz, with fans speculating it was the actor's way of sending out feelers for his involvement in "High School Musical 4."

It would be remembered that Efron and Hudgens became a couple while working on the set of the movie. The relationship lasted four years before the two stars parted ways in 2010. Since then, the two have gotten involved with other people, with Efron dating model Sami Miro and Hudgens hooking up with Austin Butler.

Nevertheless, the rumor mill is spawning talks that Efron and Hudgens are working towards rekindling their romance especially after the two have broken up with their respective partners. Fans of both stars, who played Troy Bolton and Gabriella Montez in the "High School Musical" series, are holding on to the rumors and hoping that a reunion in this fourth installment would bring them back together.

Disney has been mum about the speculated return of the original cast members that include Efron, Hudgens, Corbin Bleu, Ashley Tisdale, Monique Coleman, and Lucas Grabeel. What's certain is that "Sophia the First's" Merit Leighton is the leading candidate among those who auditioned last April. Should Leighton be cast, she will either play Erin (the only girl in the soccer team), Tamara (the school's new 'It' girl), or Natalie (a cheerleader who is also Erin's best friend).

As of now, Tisdale is the only one who confirmed that she wouldn't be returning to the franchise. She said it was "challenging" because some people had a hard time separating her character, Sharpay Evans, from who she was in real life.

"No. Looking back, it was such a perfect thing for its time and was so pure that I just don't know how you go from there," she told Daily Mail when asked if she would return.

"High School Musical didn't make us, we made High School Musical because of our friendship, how close we were, and the magic there at the time," she added.

"High School Musical 4" is slated to air sometime in 2017.