In a recent interview with Us Weekly, Ashley Tisdale dropped some "spoilers" (which he hardly count as spoilers). Here's the article
“She is a manipulator, a villain and a drama queen,” Tisdale, 22, said while promoting her Degree Girl contest (in which she’ll give away a trip to a future concert). “And she always has her eye on Troy. It’s Zac Efron - who wouldn’t?” Tisdale adds that beau Jared Murillo, 19 - who had a bit part in the sequel (they began dating in February 2007) - won’t be back this time.
Ashley also said that the third High School Musical (due in theaters October 24) is a “more amazing, more exciting and much bigger production” than the first two. Her character, Sharpay, will once again try to come between Troy (Zac Efron) and Gabriella (Vanessa Hudgens).