3) He And Luke Cage Are Partners
Despite any rivalry that could happen from them both being romantically-linked with Misty, Iron Fist and Power Man are long-time partners and best friends in the comics.
In an effort to combine the popularity of the then current Blaxploitation and Kung Fu crazes, Marvel merged Rand and Cage into one title, thereby creating one of their most perennial superhero friendships. Together, the pair formed the Heroes For Hire agency (which later included more famous names like Ant-Man, Punisher and Spider-Man).
Because of this, it has to be assumed that Mike Colter will turn up at some point in Iron Fist. If he does, it looks like Luke will be the character that knits together all the Defenders, having appeared first in Jessica Jones and then in his own series.
Perhaps he’ll call on Daredevil soon as well?