First... Do not remove iClone 5.
Unless you are having a disk space crisis, just leave it there. If you have any old projects that have trouble opening in iClone 6 you will still be able to open them in iClone 5.
Second... 3DXchange 5 will be able to import models into iClone 6.
An update (3DXchange 6) will give full support new iC6 features, and will allow export from iC6.
This is about the time where Peter (RL) will come in and provide clarification, but I think I have the essentials correct, or at least close enough to help.
iClone 7... Character Creator... Substance Designer/Painter... Blender... Audacity...
Desktop (homebuilt) - Windows 10, Ryzen 9 3900x CPU, GTX 1080 GPU (8GB), 32GB RAM, Asus X570 Pro motherboard, 2TB SSD, terabytes of disk space, dual monitors.
Laptop - Windows 10, MSI GS63VR STEALTH-252, 16GB RAM, GTX 1060 (6GB), 256GB SSD and 1TB HDD