Snark aside, Koei Tecmo may be thinking about bringing the Ninja Gaiden spin-off to PlayStation 4, supposedly as a remaster. The company filed a new trademark a few days ago for 'Yaiba: Ninja Gaiden Z' in the US, whereas back in the days of the original, only 'Yaiba' was trademarked.
As Gematsu points out, Koei Tecmo has a history of trademarking things only when it plans on actually doing something with them, so a current-gen port is naturally the first thing that comes to mind.
But why? As mentioned, Yaiba was panned by both critics and fans alike back when it launched in 2014. Unless Koei Tecmo has some serious upgrades planned, we don't see why Yaiba should ever be considered for the remaster treatment. Guess we'll just have to wait and see what happens.