There is no reason to upgrade to a new camera model because the mark IV is an improvement over the mark III (now both cameras), the 6D is an improvement over the Nikon D3s and the Nikon D700 is an improvement over the Nikon D200, and so on and so forth.
Discontinued Canon EOS 7D Digital SLR π· Camera Body Only with 18 MP CMOS Sensor
88 Review
Nikon D5100 Digital SLR Camera with 18-55mm VR Lens - High Resolution 16.2MP
172 Review
Revamped Sony Alpha a6000 Mirrorless Digital Camera: 24.3MP SLR Camera with 3.0-Inch LCD and Power Zoom Lens
103 Review
Canon PowerShot A480 camera, black
108 Review