A future upgrade of the European XFEL foresees High-Duty-Cycle (HDC) operation ranging from continuous wave (CW) and 100% duty-cycle giving maximum flexibility for the laser pulse timing to about 8% duty-cycle for high energy electrons send to the undulator sections. This requires a photoinjector operating CW. Using a L-band superconducting RF (SRF) gun cavity is the preferred solution to maintain the present 'pancake' emission scheme. Several SRF gun cavity prototypes demonstrated similar high gradients in CW like the normal conducting (NC) pulsed gun cavities used for the present XFEL photoinjector.