There's actually 3. Like Atlantis, there was a pre-Cataclysm Lemuria. It shows up in Marvel's REH / Conan stuff. In the original Tales of Atlantis that were back ups in the Subby book while Bill Everett was dealing with his illness, Lemuria and Atlantis were at war, and it was in fighting off the Lemurians, that Atlantis was destroyed.
The retcon of the Eternals ... or trying to retcon the Eternals into the MU, ended up putting the Deviants on Lemuria and making the Cataclysm all about the Celestials and Eterernals -- which I thinks sucks, but whatever. However, I'm not sure if they are now saying that REH's Lemuria was actually a continent of Deviants or not?? I think they are still saying that it was a hidden part of REH's Lemuria. Anyway, when it sank, the offshoot of Atlanteans that left the city, settled in the sunken ruins, while the Deviants were creeping around in some tunnels in another part of the continent, IIRC.
Here's some maps:
All of which goes back to one of my reasons for discounting the 2002 Tsunami Namor as in continuity. The Pacific was and has been the Lemurian sphere. The Atlantic was the Atlantean sphere. I have a hard time imaging Priest King Naga being totally okay with the Atlanteans setting in the Pacific.
Now, Parker's Oceanus ... well, lets just say the Lemurians are diminished. And IIRC, the Atlanteans HAD moved to the Pacific for the X-Men's Utopia, so it could have been like a back up, for when things inevitably went South.
You are welcome! I'd almost forgotten about it myself. Need to re-read it.
As for the Illuminati ... well, I think that was a waste for the movie. But I put it all down to fanservice. And maybe hinting at the mutants entrance.
You don't think Namor is going to be nerfed and then some in a Black Panther movie? ;p IF Namor was going to be in Black Panther, it would have been a great hint. He wouldn't necessarily have to get killed. They could have done that scene from AvX in the Namor and Wanda fight. Regardless, I still contend that Feige has zero interest in Namor and that's why we don't have him in the MCU, despite other people wanting to use him.