Would Smaug have actually followed and allied with Sauron had he lived on?

I know Gandalf was worried Smaug would have joined Sauron, but was that just him being cautious? Would Smaug actually join up with Sauron? How does he benefit from that? All it does is bring more attention to himself and gain more enemies. And if Smaug was able to be killed by Bard, I doubt he would be able to survive against an entire army, all it takes is one lucky shot, and he knows this. From what we know about Smaug, I can't see him caring for the War of the Ring either. I don't see why he or any of the winged dragons would answer to anyone outside of Morgoth.

If Smaug isn't willing to answer to Sauron, would Sauron be able to force Smaug to join him? I'm not so sure he could...I mean Sauron was taken down by Gil-Galad and Elendil, who were of course incredibly powerful in their own right, but I highly doubt they could have contended with the destructive force of Smaug.

So why would Smaug join with Sauron? Is there anything I'm overlooking here, or would he have told Sauron to take a hike while he relaxed some more.