Back to the topic:
So we have not yet for sure established whether the replacement of the press camera in the USA went over the 35mm RF or was directly by the 35mm SLR.
Am I right?
A very complicated question -
The 4x5, along with the 3.25x4.25 "Baby Graphic" cameras devolved not only to 35mm, but in the interim, to the TLR, and some medium format cameras such as the Mamiya Universal, Koni Omega, and Graflex XL, and Linhof, among others. I can remember a few photographers from the Louisville Courier Journal carrying a few Leica M series in the 60's, mostly as a personal "back up" camera. I don't think that the 4x5 just up and died one day. Rather, a lot of photographers coming up who were Baby Boomers (i.e. born 1946 and later), weren't schooled as much on sheet film, as they were roll and 135 films. As the "old timers" retired, their replacements probably brought the roll film and 35mm cameras to the job. I did some stringer work for them in the mid-1970's (Nikkormat), and there wasn't a single 4x5 in the photo gear room. When I worked there in circulation in the mid-60's, there were shelves and lockers full of Speed Graphics and their associated parts. It didn't take long, but it was evolutionary.
There were efforts during the heyday of the 4x5. Busch made a 4x5 aluminum frame camera, as did Graflex with their Super and Super Speed models. However, it was akin to adding light-weight deck chairs to the QEII, while Boeing 707's flew overhead. "Alea Iacta Est", as Caesar was alleged to have stated when he crossed the Rubicon.