With Kirby Battle Royale already on 3DS consoles in Japan & Europe, The US will be soon catching up with the rest of the world when it releases on Jan 19th. The game will consume 1,688 blocks (211mb) of space on the 3DS if you wish to download the digital version and it is now available to Pre-load.
If you do decide to pre-load the game, You will be able to download most of the game data right away and will only need a small update to unlock the rest of the content come launch day. There is also a bonus if you pre-load the game as Nintendo is handing out codes for a Kirby Battle Royale 3DS theme to deck out your 3DS home screen.
Source: 3DS eShop