My prediction has for quite some time been that Bodahn will indeed die in DAI, and I believe we might have to decide what happens to Sandal. Me? I'll be leaving him in Dagna's capable hands. Because that will be one of the options. And at some point Sandal will say, "I like Dagna" and my heart will melt.
I also agree with the person above. Sandal IS the game. He and Flemeth are by far the most interesting characters in Thedas. He might have begun life as relatively inconsequential, a little quirky colour, a weird story to add into Origins. But after everyone fell in love with the WTF moment at the end where he just happens to be there to sell you some gear having slaughtered a room of enemies, he had to come back and be more important. His various pronouncements in 2 not only tied him to Flemeth in some way, but also to Inquisition. The "not enchantment!" moment suggests he's the first dwarven mage. Whether that's part of the natural process of surface dwarves starting to reconnect with the fade, or whether it's an overture to "the magic returning" because of the events of Inquisition I cannot say.
But regardless of the controversies surrounding his awkward portrayal and what that might mean for how DA and BW represent people with learning difficulties or autism etc. (the 'savant' is a problematic image often used in an unthinking way when talking about autism and sets up unrealistic ideas about what people with autism may or may not be like), he remains one of my favourite characters and I will absolutely be a sad panda if he isn't in Inquisition.
But he will be, because he and Bodahn had specifically been invited to Orlais. That was the biggest clue right there that DA3 would be set there.