Not that this is on the horizon (yet) but I had some thoughts on who might work great as this character.
Hopefully in the process it can also mend some fences Hollywood has broken & with a disillusioned Asian community.
My first pick!
Though it's been a minute since we've seen dude - he's shown in both the first "fast & furious" flick & one of the Pierce Brosnan Bond flicks that he has an edge - and though Namor may be a good guy, he's an asshole. So you're gonna need a not so nice guy. Rick makes me believe he can do both.
Unfortunately, there are a couple issues here. Love Donnie but he is now 52! I know, he doesn't look it - but he is & they'll more than likely go the Chad Boseman route - meaning young. They'll want at least a trilogy out of this guy AT LEAST! And 52 may be a no no.
Daniel Dae Kim
I like his look but I have never seen this guy emote an emotion other than depression. Don't think he can give us the anger this character needs.
Haven't seen a lot from this guy other that crouching tiger but I like his energy. He may be too short.
That's it folks - who I'd be looking at if I were directing a Namor movie
My last option is actually more like my second - but I'd really want to Asian so he falls to last - and that Luke from the hobbit films & latest take on Dracula. Good actor but may not be threatening enough.