Republican Party: Ted Cruz, Justin Amash, Raul Labrador, Tom Cotton, Ben Sasse, Mia Love, Todd Young, Carly Fiorina, Matt Bevin, Eric Brakey, Josh Mandel (if he wins and unseats Sherrod Brown in 2018) Rick Santorum (possibly future RNC chairman)
Democratic Party: Kamala Harris, Cory Booker, Keith Ellison, Maxine Waters, Gavin Newson, Devel Patrick, Alan Grayson, Patrick Murphy
Maxine Waters has been in Congress since 1991 so she is not a future star of the Democratic Party.
So was Sanders, and he's a star now. Not as rising star, but a star. Waters is riding the social media revolution really well.