Earlier, Koei Tecmo teased that they’re working on a major update for Hyrule Warriors in Japan, and Nintendo of America confirmed this morning that Hyrule Warriors will be supported “in the long run” with this additional content in the West as well.
The first update to the game, however, will be the smaller “Ver. 1.2.0” update that is being released in Japan on September 1st. This update will be available in North America on September 26th, as a day-one update when the game launches, and will add a Challenge Mode, an 8-bit sword weapon for Link, and a BGM options menu.
More details on this update can be found in this report from earlier.
Nintendo have also confirmed that the various pre-order costumes for Zelda, Link and Ganon will be made available as paid DLC via the Nintendo eShop at a later point in time, and that they will announce price details in the future.