Nintendo of America posted a tweet announcing at this years PAX Prime that they will holding a panel for Xenoblade X which include the Nintendo Treehouse employees and Mark MacDonald from 8-4.

Because of the extra bit at the end about 8-4’s involvement for the panel, it may suggest that 8-4 could be behind the game’s localization or at the very least a part of it alongside Treehouse. If you don’t know who 8-4 is, they are a company behind many game localizations which includes Fire Emblem: Awakening, Monster Hunter Tri, Monster Hunter 3 Ultimate, Monster Hunter 4 Ultimate, Nier, Drakengard 3, Fossil Fighters: Frontier, Tales of Hearts R and Azure Striker Gunvolt.

SOURCE