With the possible exception of Mii costumes, I don't think we'll be getting any Kid Icarus series content as DLC.
Maybe it's a bold prediction, but I think Sakurai knows better than to add any more content considering they have already ported a ton of KIU content.
I also think that we'll be seeing more cross-promotion stuff. Just like how they added a Inkling trophy and Inkling Mii costumes in the DLC wave after the release of Splatoon and are now adding a Super Mario Maker stage in the upcoming wave, shortly after the release of the game it's based on.
It's worthy of note that a Dunban Mii costume (based on Xenoblade) was released in April, same month when Xenoblade 3D was released worldwide and Xenoblade X was released in Japan. Coincidence? Perhaps, it may be... Regardless, I think we might see some Xenoblade X content when the game is released outside of Japan in December.
Star Fox Zero and Metroid Prime: Federation Force may be other games that could get some content in Smash, depending on the their release schedules.