I'm torn. On one hand Brawl was almost 8 gigs and this game looks like it has much more content.
On the other hand Nintendo has been outrageously good at compression lately with their major Wii U titles all being very small, some even smaller than their Wii counterparts if I recall correctly.
On some weird radioactive third hand this is made by Namco, not Nintendo, so I don't have a damn clue what to expect.