This is the issue that I'm dealing with. I have some Thunderbolt 2 devices. If I want to use those along with the LG 5K, I lose the one cable solution. BUT, if I return this expensive LG 5K, I feel like I may be just as happy with a 4K 27" connected to a Thunderbolt 3 Dock (when they come out). One cable and all my stuff works over it. But I'm not sure. Can anyone tell me if you can see a big difference between 4K and 5K in a 27" display using the HIDPI mode in MacOS?