Certainly from an image quality standpoint, you have no reason to switch brands. Lumix's are the best value in the industry. The Panasonic Lumix DC-S1R @ $3700 for example has the 3rd best sensor in the industry right now, bested only by the Hasselblad X1D-50c @ $5700 and the Pentax 645Z at $5,000, according to DXOMark. Their sensor rating for the DC-S1R is 100. By comparison their rating for the Canon 5DMKIV camera I used for that previous image is 91. So if you've got an investment in Lumix lenses then at least for landscape photography that Lumix can't be beat at that price.So the Sony is outpacing Nikon to the level that you would ditch all your old glass? I reckon it's the combo of fast glass and contemporary body. The A7 is all the rage...What's a Lumix guy to do?
In reality though, any quality body and glass in capable hands will produce great images.