I bet the guy at Marvel that did the licensing is kicking themselves. Although I think it is not a win win for Sony either.
Spider-man became popular again because of his involvement in the MCU. Splitting him out and keeping the same actors is not really a long term strategy. They have to pull him from Iron Man and Marvel properties.
I am not sure audiences will dig that.
That said, there is little reason for Sony to compromise from a financial point of view. Disney wanted more, but Sony is not going to want to take less. And it is one of their few properties that makes money at the box office.
So, what will happen is anybodies guess at the moment. I just know that keeping or losing Tom Holland and the other cast has problems with it.
I am less concerned about who the next big brain in Marvel is going to be. Stark had that, but his charisma was the main things. He was likable. Banner, Rocket, BP (or more likely his sister), Dr. Strange and so on are all smart in their own ways.
Nobody should directly replace IM. For that matter, I do not think he was ever shown to be near Stark in terms of intelligence. The movies never showed that. He could figure some of it out but it was not easy for him. Granted, high schooler.
With time and training I suspect Peter could learn the iron Man tech
Also, Far from home makes me wonder what other security protocols tony has in place in case of his demise?
If anyone ever steals and learns to replicate the iron Man tech, especially the mini arc reactor then an armor wars shall occur.