Given that the EOS 7D MK II was launched back in 2014, a launch in 2018 makes sense as it would mean that the camera is four years old and is prime for a refresh. Unfortunately in terms of specs, not much is known about what the 7D MK III could pack, although last we heard 4K video is apparently one of the features, although given that even our smartphones can record 4K, it makes sense that the 7D MK III can do that as well.
The earlier report by Canon Rumors had also claimed that the camera could feature a “first time sensor” for Canon, meaning that it could be a brand new sensor not used in previous Canon DSLRs. In any case we guess we’ll have to wait and see when the official announcement is made, which right now seems to be pointing towards the first half of 2018, maybe even at CP+ which takes place in March.