First up, motherboard makers are ready with their Z490 board designs. So far there's been no word about the 14nm Comet Lake-S at CES 2020 and all indications seem to point to issues with Intel's 10-core Comet Lake-S part.
Secondly, while the 10-core Comet Lake-S is rumored to have a 125W TDP, the actual peak power consumption is said to be as high as 300W:
It is said that 10-core CPUs, the flagship mainstream series for CML-S, are drawing too much power, reportedly up to 300W, which is not really that surprising. Even the Core i9-9900KS draws 250-275W, but there is still some room for improvement for the upcoming 10-core CML-S part.Basically, if you want to use one of these chips you will need a good motherboard (and a decent PSU).
ComputerBase:
Several motherboard manufacturers revealed that the 10-core breaks the 300-watt mark at maximum load. Not surprisingly, the 9900KS already exceeded the 250-watt mark in scenarios of this kind. This information has nothing in common with the TDP, which is rumored to be 125 watts. Up to 4.9 GHz Turbo clock for all 20 threads on the flagship makes this value increase significantly in everyday life depending on the load.