Since Kung Lao, Kitana and Liu Kang gets a revamped look that show they are older, I really thought that those three could become alive again.

I really dont understand why not. Why the trouble to give them new look if they never appear in story mode that way?

Also, if Quan Chi is dead, all of them could also return to life. In some of chapter Quan Chi just passes out and Jax, Sub-Zero and Scorpion are not controlled anymore.

I think the part of the plot for MK11 will be Cassie & Friends freeing the revenants from Quan Chi's mind warp. How? I don't know.

Jade will more than likely be back, she was not seen as a revenant so maybe Delia freed her and now it's her turn to free the other remaining revenants with her new powers. That's what I think will happen anyways.

That's not why they returned to normal. It was because of what Raiden was doing to save Johnny. His power, mixing with whatever spell Quan Chi had cast. It didn't only save Johnny from turning, it also reversed the effect on every revenant in the room (Jax, Sub-Zero, Scorpion) rendering them human again.

Raiden also says this as Sonya is watching Jax change.