I think at some point, the definitions get blurry. 4-4-2 will not come back in its "traditional" interpretation and if it is altered almost beyond recognition, is it really "coming back"?
In general, I think it is more about roles, responsibilities and player types. You will always need players that are excellent at operating in tight areas in midfield and between the lines. And you'll always need players who can provide width. And you need players that provide depth with runs in behind or occupy the CBs. And some need to take care of the build up. Others need to protect spaces against counters (which is one reason why invented full backs became popular). But that can be distributed across different positions. Many teams still have a CM drop between the CBs in possession to build up play, others have CBs good enough at that themselves. It is rather a question of who covers who, how do they interchange/rotate with/against the ball, etc. So you essentially have different ways to get to the same result. At City, the inverted FBs allowed the CMs to attack the box more often (which is why Gündogan became their top scorer) because they pushed up into typical CM positions but this meant that the wingers needed to stay wide. This could be a way of reintroducing 10s. But you could also have the CMs stay in their "traditional" areas with the full backs pushing higher and the wingers moving inside like the inverted winger of the last 10-15 years. If you have somebody Neymar on the wing, you definitely neither want him to hug the touch line nor play him as a CM. And a FB like Davies is wasted in the center while Cancelo might be exceptional in this role.
I believe it is rather a case of the full backs pushing into typical CM/CDM positions in the build up, essentially in front of the back three. In the last decade, they rather pushed up and hugged the touch line so that the attackers in front of them could cut inside.