MFW Dark Matter has all but been reduced to a cameo boss in the Kirby series.

Kirby villains tend to stay dead (besides Magalor, but by that point the enemy was more the master crown than himself).Dark matter gets it better than most Kirby villains do anyhow, as besides the trilogy, its had numerous cameos in collectables and mini games, along with other main villains being linked to dark matter such as Dark Mind, Dark Nebula, and Dark Crafter. Also, with the recent trend of Kirby games celebrating anniversaries of past games with returning characters from those games, and the 20th anniversary of Kirby’s Dreamland 3 coming soon, we may get the full return of Dark Matter (and Zero) soon enough.