Well, there’s a difference between a canon relationship, canon TRUE LOVE, and canon end game.
I mean, Killian and Milah were definitely a canon ship. Possibly True Love (Rumple said it, so…maybe). End game? Only for Milah. Killian’s clearly gonna have a second chance at romance.
So I think you can argue that Swanfire/Swanthief has canon status–they’ve said I love you in both past and present–but that doesn’t mean it’s endgame.
Canon for me means that it’s been shown to be a romantic relationship on the show–overtly, not just hints. So I’d say that Swanfire is/was canon, Captain Swan not quite (yet). No way to tell which (if either) is endgame yet.
Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing