I don't think that a canon romantic relationship will be a thing for any of the mane six, not even Rarity - maybe an one episode thing, like her crushes on Blueblood and Trenderhoof, but nothing that lasts or gets too much focus on.
That being said, as platonic as their relationship is, soarindash is adorable and it amuses me how it's a thing that has been there since season one. People started shipping them back in the very first episode when she dreamed of shaking hooves with him in her wonderbolts fantasies, when nobody didn't even know his name. Then they've been sharing some cute moments now and then that part of the fandom interprets as shipping fuel, such as the pie saving scene at the Gala, the picture in A Canterlot Wedding, their interactions in Rainbow Falls, the "you'd be talking to me" in Rarity Investigates, the thing with the Rarity impersonation in Newbie Dash, and so on.
But that's about it and I think it's for the best that way, since shipping is almost always a sensitive issue, specially in this fandom when it comes to the main characters. So I'd rather keep looking forward to see how Rainbow and Soarin's friendship develops now that they are team mates (the Friends Forever comic featuring them as a pair made a lovely job on this btw), than them blatantly crushing on eachother.
I personally like this ship, besides them being cute together, because their personalities balance eachother well. He is a chill guy who admires, respects and praises her a lot, as much or even more as she does for him. But he's no softie all the time as seen in Rarity Investigates. He knows how to get serious and take control when the situation calls, and a stallion like this would be a great match for Rainbow. And if the comics are any indication, he has a reckless side too, and she nailed it in her own way helping him to overcome his issues. So they have great chemistry and I'll love some more eventual subtle ship tease in future episodes, but I see no blatant romance between them happening anytime soon.