YEP (that song is awesome). Apparently there's been a huge leak that we're gonna get a metal band for idols (*screams in metalhead*). This isn't just a wanted thing anymore. This is likely gonna happen : )
Other songs that should probably come back include... basically every competitive theme from Splatoon. A few competitive songs from Splatoon 2 aren't great or just wouldn't sound right in a desert. I'm mainly thinking of the band Ink Theory. They only sound right in Clam Blitz or on Shelendorf Institute, a stage that likely won't return due to how much hate it gets. Inkcoming is also a pretty disappointing song and doesn't deserve to be the main theme of Splatoon 2.
Anyway, about stages, I think I have a solid list of S2 stages that won't return.
The Reef (same fate as Urchin Underpass), Shelendorf Institute (because everyone hates it), Manta Maria (because it's in the middle of the ocean), Wahoo World (cuz why not), Golby Arena (same as Shelendorf), Muscle Forge Fitness (again, why not), either Walleye or Port Mackerel (since they're so similar), and Skipper Pavilion (same issue as the Manta Maria).
Some stages are surrounded by water but can be adjusted. I honestly think some stages could just get clones. It would be pretty funny if I booted up Splatoon 3 for the first time, and the stages in rotation were Algae Dome and Cutthroat Towers. If the Octarians can have stage clones, why can't the people of Splatsville?