Love this park! When I visited last summer the Inverter was operating. And I do believe that Disney Land was used as inspiration for the design of the park.
Definitely not going to happen. There is a better chance of CF installing a brand new B&M Invert at VF than buying Dueling Dragons or any other used B&M. And even that is an incredibly slim chance.
I've noticed that the main SF parks that still retain this charm are the three original parks, SFOT, SFOG, SFStL, which were all built from the ground up.
I personally don't think it is returning. But I could be proven wrong. We will see.
EDIT: But just to add, I don't really understand why it is that big of a deal anyway. The water fall was just a skye out affect and didn't actually get you wet. So other than aesthetics, there is no difference in the ride.