But at the end of DA2 Both the Warden and Hawke are said to have disappeared.
"Disappeared" can mean anything. Until the game proves me wrong, I maintain that "the hero was never heard from again" is just one of the oldest, most common tropes of RPG campaigns ever, to get former heroes out of the picture so the players focus on the new one, and there's nothing particularly foreshadowing in Hawke and Warden fading into obscurity once their songs have been sung. The world has simply moved on, and it's Inquisitor time.
Like I said, unless DA:I explicitely tells me otherwise, I know where my heroes are. My Warden "disappeared" in as much as he is not where Leliana thought she might find him, and the Wardens won't tell her where he went because the Commander's affairs are none of her or the Chantry's business. My Hawke also "disappeared" in as much as Varric won't tell Cassandra where he went even under torture and threat of death, because he knows Hawke is 500% done with mage/templar drama and just wants some peace and quiet, and he won't be the one to give his friend away. It's a simple case of, they're gone, but no one's telling where. They still exist somewhere out there - their friends just refuse to let the Chantry turn them into pawns for its own interests, and so they're written off as "disappeared" and Leliana and Cassandra have to look for a new hero somewhere else.
I could be wrong, of course, and that's alright too. The game could start with Corypheus sucking the souls out of the Warden and Hawke for breakfast and dropping their dead bodies to the ground like potato sacks. Cool beans, all headcanons retconned, no harm done. But as long as all we have to go by is "disappeared" and no solid resolution is ever given, I'll keep my endgame scenarios. They fit my characters' stories better than any conspiracy theory.
I've gone off-topic enough, though. Back to Grey Wardens in Ferelden, and such.