Newey has always been clear he wasn't interested in moving to Italy because he wanted to be around his children and grandchildren etc, and his wife wanted to remain in England. To do such a technical role you need to be regularly at the factory where the cars are developed, which is why John Bernard never suceeded at Maranello when he was designing their race cars. Not sure how true, but Newey was asked about a new challenge at Ferrari and he didn't shoot the idea down like he had previously. If Christian does leave Red Bull and their contracts have that clause, it could be an option. It depends whether Adrian wants the challenge this late in life as he's in his 60's now. There is the option to work with the most successful F1 driver in history though and it would be a very worthwhile role financially I would imagine.
As the star designer of the 80s, part of John Barnard's deal with Ferrari was the establishment of the Guildford Technical Office (GTO) design office. Aside from not relocating to Italy, the way he did things rubbed some people the wrong way.
But the 640 was a pretty car, and ushered in the paddle-shifted semi-auto gearbox.
The GTO facility later served as McLaren's first road car factory, where the F1 was produced.