Sanji is Pudding's first love.
She will mature, realize that people shouldn't treat her as some freak, and that are people out there who genuine will like her for who she is. Sanji is just the first person to make her realize that. He will always have a place in her heart, but as time passes, she will meet other people who treat her well, and will eventually find her true love.
Sanji and Nami are never gonna get married or anything.
They will live as some bachelor vibes, but they will always come back for each other. Think of it similar to a Batman and Catwoman relationship. They might have some short relationships along the way, but their hearts will always belong to each other.
The end.
:P