We now have a timeframe.
Bloodstained: Ritual of the Night has its latest release window.
During today's Nintendo Direct, it was announced that the platformer will be coming to the Nintendo Switch this summer. A new trailer has also been released showcasing gameplay:
Originally scheduled for a 2017 release, Bloodstained has been pushed back a number of times, most recently into 2019. Development at one point moved from the Wii U to the Switch.