It should depend on what the board is rated for. A board rated for a 65watt CPU should run a 32core 65watt part. From what I've seen the 7nm chips use only slightly more power than the 14nm parts.
From some basic calculation and some extrapolation, the top end X470 boards should handle a 16core cpu no problem even overclocked, the Crosshair VII hero, Taichi and Aorus gaming 7 are all fine for such a chip if it ever shows up.
It kinda makes sense why we see overkill VRM design on these boards.