If you want to have the game digitally, you can already make room for free.
Although it will take some time before we can get started with Super Smash Bros. Ultimate, the official Japanese Nintendo Store has already provided an estimate of the amount of storage space you will need when you purchase the game in the Nintendo eShop. According to Nintendo, you will need about 16 GB if you want to install the game on your Nintendo Switch.
Is that big?
If you look at the larger games now on the Nintendo Switch then you are talking about titles like; Doom, Wolfenstein, and yes even Breath of the Wild. These are all games that use a 16GB cartridge. Outside of Zelda it is also games that do this and still need a hefty download.
From a Nintendo perspective, however, it is certainly large. A lot of titles are secretly only a few gigabytes in size. Smash Bros. Ultimate is in the size categoryof BOTW. So we can prepare ourselves for a lot of things.
We have to wait a few months for the launch of Super Smash Bros. Ultimate and the game is almost certainly still under development. That means that at the moment it is actually impossible to indicate how much space will eventually be needed for downloading the game. By the end of 2018, we will probably receive more precise data.
But we also actually see the opportunity for DLC when it comes to Smash Bros. Ultimate.
Super Smash Bros. Ultimate appears worldwide on December 7, 2018.