Fire Emblem: Awakening has been a great success for Nintendo, not just in terms of sales but also in terms of how much downloadable content has been purchased, judging by early figures from Japan alone. Intelligent Systems designed Awakening’s DLC in the form of various add-on chapters that provide various optional benefits as well as the occasional side-story.
Why then, was Shin Megami Tensei X Fire Emblem not a part of the DLC plans for Fire Emblem: Awakening? It would’ve made sense—both Awakening and Shin Megami Tensei IV are Nintendo 3DS games, and both have been very successful.
Nintendo’s Hitoshi Yamagami, who is overseeing Shin Megami Tensei X Fire Emblem, tells the Hobby Consolas magazine that it’s because Nintendo felt that it is assumed DLC should be based on the game it’s being included in, and provide more content for existing fans, instead of disappointing them with something excessively different.
Yamagami went on to say that, if you intend to do a collaboration like Shin Megami Tensei X Fire Emblem, which is intended for a different audience, it’s best to keep it separate from the main game, pointing out that the crossover and the DLC were very different from one another.
As previously mentioned, Yamagami hinted that Shin Megami Tensei X Fire Emblem will take place at least partly in the modern world, so it makes sense that the game isn’t aimed at the exact same audience that enjoys traditional Fire Emblem games.
Source: Fire Emblem WoD