The game is now slated for a western release in North America and Europe for PS4, Nintendo Switch, and PC in early 2019.
As previously announced, the game will lose in the west its PS Vita version that will be released only in Japan, but I doubt many will be overly surprised by that by now. The Japanese release is scheduled for PS4, Switch, and PS Vita on September 20th.
The game retells the story of the original and super-popular visual novel Steins;Gate by mixing the original art and cutscenes from the anime series that aired in 2011, basically bringing the player the best of both worlds in a rather original remastering operation. That being said, there will be new anime scenes created specifically for the game, since the anime did not show all the routes (quite obviously).
If you want to see more about the game, you can check out the original announcement trailer from March.