Here:
https://www.nintendolife.com/news/2...ssibility_of_smash_bros_ultimate_demo_and_dlc
"Obviously that was a big part of the Wii U game, but part of Mr Sakurai's approach is really focusing on getting the game done, and then once he has the game done, he'll start to make some decisions about what he wants to do with other characters or DLC, things like that. Whether or not he decides to do DLC again, or whether or not he decides this is the ultimate edition and there's nothing more I can fit in there - we'll have to see as we get closer to launch."
-Bill Trinen (emphasis mine)
This may get ignored because DLC is practically assured by users here.