We're told that the Canon EOS 6D Mark II will be announced in July of this year, though the exact date is unknown at the time of writing this. The EOS 6D Mark II will also start shipping relatively soon after the announcement, so it's safe to say you should have your hands on the new camera some time in August, 2017.
Specifications have been extremely hard to come by, and anything out there currently is either made up or just logical features we can expect in the coming body.
We posted a predicted specifications list back in February, but it's nothing more than conjecture at this point.
We do expect legitimate specifications to leak out in the coming month or so.
We put a [CR2] on this because announcement dates can move, though it's more common with lenses than with camera bodies.