https://www.gamespot.com/articles/sega-genesis-mini-delayed-to-2019/1100-6461864/

The Sega Genesis Mini has been delayed to 2019. Originally announced with a 2018 release date, the little system is now scheduled to arrive next year, Sega announced in a tweet.

Gematsu translated the Japanese tweet and quotes Sega as saying it decided to push back release in part to allow the company to launch the console around the world simultaneously.