It’s been a while since Super Smash Bros. for Wii U and 3DS had an update, with the last patch being released March 15th earlier this year. We should be seeing a jump to version 1.1.6 soon though, according to the official Nintendo of Japan website.
Chances are this will be a minor update on par with the last, simply introducing some character balancing tweaks. Hardcore fans will no doubt write up a list documenting the specific changes and how drastic they may be soon after its release. The patch will need 61MB of space on the Wii U, and 325MB on the 3DS.
As per usual older replays will also become unwatchable after the update, so be sure to back them up or upload them as soon as possible!