The new 6D Mark II is a 26.2-megapixel, full-frame CMOS sensor, up in resolution from the 20.2MP in the original 6D. Paired with a DIGIC 7 Image Processor, the sensor can capture an ISO range of 100 to 40000 (up from 25600 in the Mark I) and perform at high speed continuous shooting at up to 6.5fps (up from 4.5fps in the original 6D).
With an autofocus system featuring 45 AF points, all of them being cross-type points (the original 6D had 11 AF points with the center being a cross-type point). The Dual Pixel CMOS AF on the sensor provides phase-detection autofocus during Full HD video recording at 60p. Did Canon give 4K capabilities to the new 6D? No and it's confusing why they would skip on this feature.
The 6D Mark II will be available starting in late July 2017 with a price tag of $1,999 for the body only, $2,599 when paired with the Canon 24-105mm f/3.5-5.6 STM, or $3,099 when paired with the Canon 24-105mm f/4L IS.