Here's something I never thought about. The Ice Climbers weren't in Smash 4 because they couldn't run on 3DS, but I don't think that's the only reason.
People forget about 8-Player Smash. 16 Ice Climber models would be AWFUL on the game and would cause awful lag.
As much as I REALLY want them back, if 8-Player Smash returns in Smash for Switch, I don't see them coming back.
Just think... do you really think 8 Ice Climbers (16 models) on a big stage would work well... and never mind all that on HANDHELD MODE