I’m in exactly the same place, unfortunately.
I’m not sure why Mendes would want to return - I didn’t see enough in SP to indicate that he has much more to give to the franchise, (and I love SF and give Mendes great credit for that). For no-one sake’s but history itself, I’d rather he stated that he was done with it.
The franchise does seem to have a habit of going a film to far with its directors - there’s a case to be made that for Hamilton, Gilbert, and even Young, their last film is their weakest, or in Young’s case, uneven. I’d offer that onlly Glenn was able to end on an upward arc, with TLD and LTK providing a positive bookend to the puppyish enthusiasm of his debut.
A new script (if that’s what’s in the works) and a new director would be best for the franchise. And I think the lure of doing DC’s last is almost as attractive proposition as introducing a new actor.