I'm not sure if this is to say that the five DLC characters will be purely Nintendo focused or if they did have an outreach to the third party to make their picks.
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Knowing our luck though, I wouldn't be shocked at all if we get the main character from the Fire Emblem: Three Houses game as one of those five. Say what you will, but if we got Corrin as quick as we did as DLC, it wouldn't fall out of the realm of possibility of them doing that again.
Still, I stand by Sakurai for whoever those five characters will be. I feel like he has a good understanding of what the fans are looking for and as he said: " he decided if they can create a fighter based on Nintendo's selection, then came up with the plan" that they were going to follow. Hopefully those expectations aren't too high by fans, but I know if we did get one or two shocking reveals, alot of people are probably going to love Nintendo all the more.