Okay, a lot of those are awesome answers, but I'll reply here for clarity.
I think it'd be a reach if he made it to M41, and if he did, he's certainly not important. Legion First Captains are serious business, and I know some of them are still kicking at that point, but I'll be 100% honest, no, Sevatar doesn't survive into the Dark Millennium.
He has an arc. I worked it out with Alan Bligh a while back. He has a future, and I'm pretty sure we'll see it in some form within a few years. But his role in the Horus Heresy is pretty much just his prologue. His real story is in the years after the Horus Heresy. And it's probably not a spoiler to say he's never going to be a great hero on either side of the Traitor/Loyalist divide, with his name echoing gloriously into eternity.
Sevatar is seeking righteousness, in a way. He has a line at some point (I think it's to Altani or the Sin-Eater) where he says "I'm not on anyone's side." And that sums him up, not because he's some badass space loner, but because the structures within which he's matured and fought for have, by and large, failed. Not failed him. Just failed. At least from his perspective.
And his arc is a response to that. Can't really be too much more specific, sorry!
Hope that helps a little!
ADB가 AMA 할때 헤러시 끝나고도 살아있을거고 뭔가 이루긴 할꺼라고 답변했네
웬지 세바타로 블레기 떡밥 풀거나 그나 맴버가 되었다는 떡밥 만들 필인데. - dc App
나로도 레가처럼 창백하고 눈알 까맣다는 말이 있어서 걔네는 아닐듯.. 순교자가 되지 않을까/
아니면 그나 맴버중 하나가 되거나. 정체 안 밝혀진 그나 맴버도 몇몇 있던데. - dc App
그나 중대장 한 자리 비었으니 거기 들어갈 수도 있겄네
그나 나로 출신은 테라출신 사서가 되는거 확정아님?
세바타가 살아 있다!!!! - dc App