[NAME] If you assume that the fan/heatsink that comes with the i5-10600K is adequate for that processor based upon its Thermal Design Power (TDP) then the answer is yes it should adequately cool the i7-10700 and i7-10700K. The TDP of the i5-10600K is 125 W, the TDP of the i7-10700 is 65 W, and the TDP of the i7-10700K is 125 W. If I were going through the effort/expense of upgrading the processor I think I would spend the extra money and upgrade the fan/heatsink at the same time. 
Will the fan that comes with the i5 properly cool the i7 and its k version if I upgrade processor in the future? 
XPS 8940 - Upgrade from i5-10600K to i7-10700