On a side note, something I think is worth taking note of. As we know now, Chrom was considered for Smash 4, but Sakurai and his team couldn't figure out a character concept that didn't either feel out of character or leave him feeling like a retread of Marth and Ike. Meanwhile, Robin was slated for inclusion very early in development, at least according to
what we've been shown of an early project proposal.
On their own, they're interesting facts...but combined, they seem to say that
Robin and Chrom were probably considered independently of each other. It wasn't one or the other, it wasn't "one Fire Emblem slot", they could've
both made it had Chrom's circumstances and abilities been different.
Which gives us even more reason to believe Sakurai has no problem doubling up on newcomers from the same franchise or even the same
game if both newcomers are compelling enough. That bodes well particularly for Sun and Moon.