New Fiesta has same engines as old model.
I think Duratec HE is discontinued though.
There's really nothing wrong with using the same platform, engines, chassis etc from the old car to the new car if there's nothing wrong with them.
It's called "top-hatting"
Developing the car costs a lot of money, why spend on new when the old one "aint broke".
EG: The dash board/fascia/instrument panel (whatever you want to call it) on the Jaguar XF cost $35,000,000 to develop for LHD and $20,000,000 for RHD.
And that carries over the whole steering column/shrouds and switches from the S-Type and the steering wheel is carried over from the XK and the Nav Screen is Cross Car Line.