A few days ago, Game Source Entertainment, a Hong Kong game distributor, listed Ninja Gaiden Trilogy for PlayStation 4 and Nintendo Switch.
This listing was quickly removed, but we can still visit a cached version of the page, corresponding to the Switch version. This page contains a link to the PS4 Ninja Gaiden Trilogy game.
If we read the description, we know that Ninja Gaiden Trilogy for PS4 and Switch would include Ninja Gaiden Sigma, Ninja Gaiden Sigma 2, and Ninja Gaiden 3: Razor’s Edge. However, Koei Tecmo has not officially announced this compilation.
Via | Gematsu