How many years......

The lens of the XS-1 will not cover the larger 1", 4/3 or APS-C sensors. Besides with larger sensors, it no longer reach the 35mm equivalent of 624mm. 1" sensors have a 2.7 X crop factor, m43 have 2x and APS-C have 1.5 X crop factors so even if the XS-1 lens could over a larger sensor without vignetting or soft corners (unlikely), you'd loose much of the reach that the higher crop factor of the 2/3" sensor provides.

I'm fortunate enough to own the D800, and personally, I don't think tiny sensors will ever be able to match the IQ of the larger FF sensor of that camera.  The physics just don't work for the smaller sensor as you'll never achieve the extremely low SN/R of the larger sensor so images over base ISO will look worse, and you'll never be able to isolate subjects like a FF camera as DOF on the smaller sensor is extremely deep.