The military will fight any enchroachment on their land or airspace.
With Miramar, people see all of that land and say, “Look, plenty of space for an airport.” However, those same people have no idea what the air traffic patterns are like and what adding heavy civilian traffic will do to operations. Further, the military will not be adding any more space or bases in SoCal and it is not possible to predict how much space we are going to need in the future for effective defense and training.
The word at Miramar is that there will be no civilian airport there. I don’t know what they are saying up at Pendleton but it is probably the same thing.
My personal OPINION is that an airport should be built in Ramona and either the 67 should be expanded or a new road/freeway should be built through Poway. Or we could be like the Japanese and build a sinking island (just kidding).