Huh, that'd be something. I've been waiting for Nintendo to release that Kirby game for years. Or hell, to even show it again or at least acknowledge its existance. It was part of that late batch of GCN titles along with Super Paper Mario, DK Bongo Blast. The two former were brought up to Wii, but Kirby's just been MIA forever. It was shown off with Mario Baseball originally back in like... 2004, and I think they showed it at E3 that year, but that was the last we heard of it.
But yeah, really hoping for it to come. 4-player Kirby sidescrolling is something that should've been done a lonnnnng time ago.