We still play it semi-regularly but after the initial release on the PS4, they left it to die, with barely any new releases at all. They did a token gesture of getting some of your old songs over from the PS3 but yeah, I don't think they were prepared for all the problems that would cause.
I think pushing it to mobile as well, made sense, but didn't work half as well. There was something cooler and more fun about singing into the microphone than holding up your phone. We still play with a pair of wired PS2 mics.