Luffy would have someone else save him. Sanji's a weak character. Most people don't watch one piece for Sanji. Only way he is relevant because he is compared to Zoro and fetishized by fujoshis/gay fandom.
Well yeah, I've compared Oda to Sanji before and joked he's Oda's self insert too. It would make a lot of sense given how openly/proudly perverted Oda is. It's funny how Sanji rescued Nami from a forced wedding and then he was forced into one too, with Nami being relevant in that arc trying to save him too. But he ended up carriyng Nami again funnily enough too! And then there's Lola connecting both of those arcs directly...WTF ODA!? Way too big brain!
And the most obvious detail, sanji only called Nami with the honorific "San", and Nami only calls sanji with an honorific
To be honest even though I don't care about ships and all that shit, sanji ending up with Nami seem like the most likely couple, heck even toei ships them, these fuckers even spoil Manga readers so I wouldn't be surprised if sana happend by the end of the story