New stages or an adventure mode though I would say fits into "upgraded port" territory. When I hear "new game" that brings visions of redeveloping and slowly announcing previously existent characters, etc. like had to be done for Melee/Brawl/WiiU.
I'm expecting it to be Smash 4 base like Splatoon 2, but to be considered Smash 5 (or 6 is you count 3DS). By calling it Smash 5, it'll allow them to take a base and cut/add stuff to it. If you get a championship edition, you should have stuff only added and tweaked. Smash 5 means you can cut or add to your desire. And feed drip info isn't necessary with returning characters. They can have a huge character based intro to the game coming to Switch- showing off all returning characters then start the new info feed drip.
But I'm OK with a Championship Edition if they add all the DLC, give Cloud his English voiceover, add a Subspace like story mode and some new characters and stages. Ice Climbers can finally return.