The Fire Emblem series is notoriously difficult, in large part due to its permanent death. Fire Emblem: Awakening was a kinder, gentler game with the addition of Casual Mode that simply tags defeated characters out for the duration of a battle. Apparently it was a big hit among the staff, and they say future games are likely to include it as well.
In a developer interview from Nintendo, several key staff members talked about their own experience warming up to Casual Mode. Nintendo director Genki Yokota says that after being skeptical, he now plays exclusively on Casual. While he claims the addition would depend on the play style, he says he's "pretty sure" they would include the mode.
"In the end, you have people who really love the characters, and they don't want to lose them permanently when they save their progress. So that's why we added it, and I don't mind it being there," he said. "But on the other hand--and this is just a hypothetical example--let's say we wanted to depict a really big and serious war scene. In a situation like that, having permadeath would help lend weight to everything; it'd be much more tense and meaningful to players if their characters' lives were truly on the line, just like in a real war. So it really depends."
That sounds more like Casual Mode would be situational if they wanted to create more tension, but given that so many of the heads appreciate the easier mode it's probably not going anywhere.
The team also briefly touched on DLC plans, as project manager Masahiro Higuchi noted there are "no plans" for another round after the initial two.