Someone has already created an Elecraft-K4 list, and it is active.
I have no objection to Elecraft-K4 discussions on this list, as they are providing some information as to whether one should upgrade from a K3 or K3S to a K4, and is valuable information.
At some point, we may decide to restrict discussions to the K3/K3s, but for now while the concept is new, feel free to post comparisons of the K4 to the current K3/K3s line._,