The maximum (without virtual channel support) is still 6 cameras, x4 2-lane MIPI/CSI-2 and x2 4-lane MIPI/CSI-2. With virtual channel support the maximum would be 16 cameras.
Virtual channel support has been added recently, RidgeRun has expertise on GMSL/FDP-Link III Ser/Des cameras and virtual channel use cases. Feel free to contact us in case you need professional support.