The iPhone 9 camera will likely be the same as the iPhone XR or higher. Apple's line up for 2020 will be quite impressive, with something for everyone. The $399 model for a capable, but inexpensive iPhone, the 5.4 inch model for those wanting a smaller form factor, and the 6.7 inch for the folks wanting a maxed out phone with a very large display. My guess is it will be something like this, with all other phones retired:
$399 iPhone 9 3GB RAM, 64GB, A13, TouchID, LCD, LTE, single camera
$499 iPhone XR 3GB RAM, 64GB, A12, FaceID, LCD, LTE, single camera
$599 iPhone 11 4GB RAM, 64GB, A13, FaceID, LCD, LTE, dual cameras
$699 iPhone 12 5.4 inch, 4GB RAM, 64GB, A14, FaceID, OLED, 5G, dual cameras
$799 iPhone 12 6.1 inch, 4GB RAM, 64GB, A14, FaceID, OLED, 5G, dual cameras
$999 iPhone 12 Pro 6.1 inch, 6GB RAM, 128GB, A14, FaceID, OLED, 5G, triple ToF cameras
$1099 iPhone 12 Pro 6.7 inch, 6GB RAM, 128GB, A14, FaceID, OLED, 5G, triple ToF cameras