Yes, it's really going to happen.
A few weeks back we learned about Ford's major restructuring plan that involves serious reductions in small car production and a greater focus on developing EVs, hybrids, and trucks. For example, the Fiesta and Fiesta ST hot hatch will soon be dead in the US. Cost-cutting measures such as that allows Ford to re-direct resources towards new projects like Team Edison, its newly created and cleverly named electrification team. But vehicles such as the Mustang and F-150 aren't going anywhere.
In fact, they'll soon be updated for the next decade. Car and Driver has learned that as part of the planned 13 new electrified vehicles in the next five years, both the Mustang and F-150 will receive hybrid tech. Specifics aren't known at the moment, but we figure Ford will utilize, say, a turbo four-cylinder and link it up with a hybrid system for each vehicle. A hybrid Mustang must deliver on customers' expected performance levels, while a hybrid F-150 needs to be a proper truck without exception; bolting in any old hybrid system is unacceptable. Ford is fully aware of this so chances are both will deliver the goods.
Considering the Mustang and F-150 have just undergone their respective mid-life refreshes, chances are we won't see the hybrid versions of either until the next generation models arrive. That would make complete sense because neither of the current vehicles were designed from the get-go to accommodate hybridization. Obviously that'll be changing. As of now, the upcoming reborn Ranger and Bronco, due in 2019 and 2020, respectively, won't offer a hybrid option, but that could change. In any case, the iconic Mustang and F-150 aren't going anywhere. They're just be adapted to fit the times.
As for the Mustang's V8 option? Good question. Ford hasn't said anything to the contrary, but it's a good bet V8 power will be sticking around for a little while longer. Remember, Ford has already dabbled in extreme twin-turbo V8 performance. It's called the GT.