The Netflix side of the Marvel universe continues to expand—despite the recent fan-crushing revelation that a Punisher spin-off isn't happening—with second seasons of Daredevil (coming later this month) and Jessica Jones (not coming soon enough, because no date has been announced). And as you already know, the Luke Cage series is also on the way. According to reports there's talks of another hero hitting the Marvel Netflix universe soon via the aforementioned Luke Cage series: Iron Fist.
It was a only a few days ago that Iron Fist's reported casting caused fans to freak out, and not in a good way. Netflix hasn't confirmed the news, but Finn Jones is rumored to have been cast as Iron Fist upsetting fans that Daniel Rand or "Iron Fist," a martial arts master, would be played by a white guy (as is usually the case). Jones is currently playing Ser Loras Tyrell on HBO's Game of Thrones, so if this casting is true it may mean his time on GoT is almost up.
ScreenCrush reports Heroic Hollywood's Umberto Gonzalez said Iron Fist would appear in the Luke Cage finale ahead of his own standalone Netflix series. "Yes he is. Episode 13. That's why it was announced, or else it would have leaked…They shot him last week," said Gonzalez, even providing when he'd appear (at about 19:50). ScreenCrush however notes that this may not pan out as Matt Murdock was rumored to cameo in Jessica Jones and that never happened, though there was some Daredevil crossover,which I won't spoil but you're doing yourself a disservice if you don't watch Jessica Jones.
(Spoiler ahead) Jessica Jones already teased the existence of Iron Fist along with "99 gifted friends" in Manhattan alone, so introducing Iron Fist in Luke Cage would just up the excitement ahead of Netflix's The Defenders series.
The rumor mill will run wild for a while. Try not to get carried away.