Every time people bring up Daggerheart as a fantasy heartbreaker that will get no support (as evidenced by nothing, I will add), I'll point to the DC20 RPG as the 100% better example example of a game with no future and supplying no real reason for anyone concerned about a game line to buy the core book.
DH will sell like gangbusters in its first year or so of life and its future will be fueled by an actual play from the world's most popular actual play streamers. Beyond that, I've no idea if it'll be any kind of perennial seller but I wouldn't be surprised if it was.