Game Source Entertainment, a distributor in Hong Kong, has listed Ninja Gaiden Trilogy for both PS4 and Switch. The listing has since been taken down but a cached version of the listing for Switch exists here courtesy of Gematsu. We will have to wait and see if Koei Tecmo announces a Ninja Gaiden Trilogy of some kind.
In the meantime, stay tuned at Final Weapon for the latest Japanese gaming news!