How successful will the show's actors will be post-GoT?

For most of them, I think the SF convention circuit will be a major source of income.

Past GoT actors seem to pop up in many Netflix movies or shows, most notably the Red Viper was in Triple Frontier with Affleck. Might not be A-List roles, but enough to keep them working.

Richard Madden has probably had the most success so far post GoT. The lead in two series, the second of which earning him a Golden Globe, and Prince Charming in Cinderella.

Lena Headey already had a level of fame prior to the show. Peter Dinklage will always be around, even though we'll only ever really remember him as Tyrion Lannister. Emile Clarke will do well, and already has, in part because she looks so different from her character.

Everyone else will have varying degrees of success.

Aidan would be fine without this show. He was already a main character on The Wire.

I think Nikolaj Coster-Waldau is a particularly good actor - how successful he'll be depends on many factors which have little to do with his acting ability.

Peter Dinklage is another decent actor but he has a severe handicap of sorts - so the number of roles he can apply for is limited.

Most of them are British so at least they will be all right at home. Which is good because of the opportunity to take normal roles. That, of course, applies only to actors, so Emilia Clarke and Sophie Turner are on their own.

I think most of them will work as steady as they want...maybe starring in Indies and co starring in main stream. Hopefully sticking with cable for any tv work..
It's not like being an A list actor is the only path to success. There's not that many at the very top, it makes people crazy and there's nowhere to go but down.
And being in GOT is success already in itself ..

You forgot Sophie Turner, she is starring at the moment as Jean Gray in Dark Phoenix which is an X-men franchise.

She was already in X-men: Apocalypse but I think in Dark Phoenix she is the main character.

Marvel movies are really popular these days, so I think she has a promising career after GOT.

John Snow - Will hang around for a while but likely will never have another gig in the realm of his run on GOT. His most notable attempt at a starring vehicle 'Pompeii' didn't go over well.

Arya- Will never be a big star. Will mostly do independent film and television.

Sansa- Hollywood is giving her a shot but I feel she doesn't quite have the talent or charisma to have a successful career as a leading lady

Cersei- Was already a seasoned & reasonably successful actress before GOT. She will be fine

Daenerys- The most successful career of the young relative unknowns who made it big on GOT, showing range and versatility in other roles. Likely also bennifits from looking very distinguished from her GOT character with her natural hair. The most successful outside of GOT so far and probably will continue to be so.

Jaime- An experienced actor who may never be a big star but has enough experience & range to maintain a steady, middling career beyond GOT

Tyrion- The most successful dwarf actor in the business. I imagine he will continue to be around but likely won't come close to achieving the level of success he has had with GOT.