An interview with Bungie's community manager signals that the developers have thought about it at least.
Bungie has mentioned that Sparrow races are "definitely one of the things that has come up as a topic" during their discussions.
"It's definitely an idea that has come up at the studio," he said. "And there are dozens and dozens and dozens of cool ideas. Part of the process of sustaining [Destiny] is figuring out what's the most bang for the buck, what's the right feedback to go after and address, how do we deliver the experiences that players want. And race is definitely one of the things that has come up as a topic, so we'll see."
Players are already holding their own unofficial Sparrow races in the game, with their own leagues too.
I called it in my review of Destiny, Sparrows are fun to roam around on, and official racing mode support for them would definitely be something I would enjoy, at least.