Sparks Fly has been the "current single" for 75 days now... In comparison, Love Story had 88 days between its release and the release of White Horse. You Belong With Me had 132 days between its release and the release of Fifteen.
Love Story had a great music video, pop adds, promo performances and hype as lead single.
You Belong With Me also had a great music video, pop adds and promo performances.
Sparks Fly has a tour video, no pop adds, no promo performances and little hype.
At this point, I think there's two ways to go about this.
1. Give Sparks Fly 3-4 more weeks before cutting the losses and move on to the next single; Sparks Fly would still be a top 10 hit (maybe even top 5), and the next single- hopefully Enchanted- gets a big start with a live performance at the CMAs the first week of November.
2. Give Sparks Fly pop adds and drag the song out for as long as possible, with a live performance at the CMAs in November. By the day of the CMAs (November 9), Sparks Fly will have spent 115 days as the "current single" and it'd probably get another month or two after that. Doing this runs the risk that the song won't do well on pop radio.
I think the first option is the smarter choice. Like I said, Sparks Fly gets to be a top 10 country hit, and the next single will get a strong start. I don't think it's appropriate to spend 5+ months promoting a single that isn't a massive hit; Mean was only a single for about 3 months before Sparks Fly was released, and Mean got more airplay than Sparks Fly is getting...
If it were up to me, I'd give Sparks Fly until mid-October so that it can peak in the top 7 on country radio while Enchanted continues to gain popularity with the Wonderstruck promo campaign, release an Enchanted radio edit during the last 2 weeks of October, perform Enchanted at the CMAs November 9th and release the Enchanted music video (the Wonderstruck commercials) in mid-to-late November.
Give Enchanted its chance to shine, because the reality is that Sparks Fly is not going #1 no matter what the label- or the fans- do.