The development of Metroid Prime 4 has started from scratch with the support of Retro Studios, a situation that will obviously lead to a considerable delay in the development time of the game. Despite this, the game would not come out in 2019 according to an insider, Liam Robertson.
Robertson says that Nintendo had, in fact, no plans to launch Metroid Prime 4 in 2019 and after all the game has always been announced as “TBA”, or with a launch window to be announced, and never has there been a specific period for the publication of the project.
There are no other details about it, in the last few hours Nintendo has announced the reboot of the project, the development of the game has started again with the help of Retro Studios, the development team of the original Metroid Prime trilogy released on GameCube and Wii between 2002 and 2007. In all likelihood the work done by the new development team (created specifically to work on Metroid Prime 4) was not considered up to expectations, hence the decision was to stop the work and start again.
There are no precise timing for the release of Metroid Prime 4 but it is not excluded that the project can take at least three years of work, we will hardly see the game in stores before 2021/2022.