Most/all early TR boards were "gaming" branded/targetted, and those typically have power headroom for overclocking. It's certainly possible some of the early boards won't be able to support TR2 at full spec speeds, but I would anticipate most being able to.

2nd Gen TR will draw ~250W. X399 boards have at least 1x 4-Pin and 1x 8-Pin ATX-12V connector, so at least 225W. The rest is supplied by the ATX 24 pin connection. Some X399 boards use 2x 8-Pin ATX-12V connectors, that works out to 300W, which should be more than enough for Threadripper 2.

I'm just relaying what I read when they announced the TR2. Which seems to be copy-pasted to amongst the tech news sites.

Unfortunately they just state "... some first-generation X399 motherboards may not be able to deliver enough power..."

And not specifically which.

https://arstechnica.com/gadgets/2018/06/amd-unveils-threadri...

If their statement is false then that's on them.

That’s only the 32core And perhaps 24core TR. the 8-16 will probably be lower than current due to node shrink.