As far as I found out today, the first season is indeed going to be 2026/27. But as of now, there won't be too many changes for the top nations on how they are going to plan the international breaks.
Because of the relegation system, there could be a benefit for smaller nations in the future to get the chance to play against bigger nations than before.
But some see it more as a marketing gimmick and concession to small nations than as a groundbreaking innovation by the IIHF that's going to benefit everyone.
Furthermore, each tournament host will receive €50,000 and €10,000 will be distributed to the participating nations.
That's all I have for now, but I hope to get more information soon - hopefully directly from the IIHF.