Samsung had planned a tri-folding phone with four rear cameras but cancelled it. Recently, a leaked image from Omar Saheb, VP Marketing & E-commerce at Samsung Electronics MENA, showed the Galaxy Z TriFold with four cameras instead of three. The camera on the bottom is thinner than the others, suggesting it’s a prototype for the original design.
The phone has a 200MP primary camera, but some fans wanted better ultrawide and telephoto cameras. A fourth camera with a 50MP sensor and 5x optical zoom could have enhanced imaging capabilities. This image appears to be one of Samsung’s early prototypes before finalizing the Galaxy Z TriFold design.
Source: https://www.sammobile.com/news/galaxy-z-trifold-prototype-four-rear-cameras