Sega Mega Drive Mini Retro Gaming Console Delayed Until 2019
The Mega Drive Mini, which will be called the Genesis Mini in the United States, was originally supposed to launch [initially] in Japan later this year. However, we’re now learning that the Japanese released won’t occur until sometime in 2019, with the U.S. and European launches coming later.

Unfortunately, the Twitter post that announced the delay doesn’t provide any specifics on the new release date. More importantly, there are also no indications about what games will come preloaded with the console. But given the precedent set by the NES Classic and SNES Classic, we should expect around 20 popular classic titles to be loaded onto the machine.
【お知らせ】セガフェス 2018で発表した「メガドライブ ミニ(仮称)」の発売を2019年に変更いたします。本年発売に向けて開発を行っておりましたが、特に海外のお客様からの反響が大きく、改めて北米は“GENESIS”、欧州は欧州版”Mega Drive”を再現したモデルを準備し、全世界で同時期に発売予定です。
— セガ公式アカウント (@SEGA_OFFICIAL) September 19, 2018
It should be noted that the Genesis Mini will be joined in 2019 by the aforementioned Atari VCS. Preorders for that console quickly surpassed $2 million on Indiegogo and it will begin shipping in July 2019.

In the short term, Sony just announced that its PlayStation Classic mini console will ship on December 3rd. It comes with two controllers in the box, 20 preinstalled games, and will be priced at $99.