Galaxy Z Fold 4 will have the same body as the Galaxy Z Fold 3, which it will replace. As far as has been stated, only minor improvements will be made.
The S-Pen stylus will almost certainly be the most significant change for the Galaxy Z Fold 4. Like the Galaxy S22 Ultra, the phone will most likely include the S-Pen pen.
The Galaxy Z Flip 4's vertical structure will be similar to that of the Galaxy Z Flip 3 it will replace. The screen on this model will be 6.7 inches on the inside and 1.9 inches on the outside.