Maybe they'll attack and maybe not. Again, not every dragon you see is hostile. I've also had dragons come in and circle over the road outside Whiterun for several minutes, with myself and numerous guards running around shooting at them, and even with all that provocation they didn't attack. Eventually they just flew away, no harm no foul no blood no ambulance.

These days I usually don't bother going after a dragon until it either registers as hostile on my own radar, or I can clearly see it attacking someone or something else. I may stand and watch it or follow it for a while to see if it's going to do that, but I don't waste any arrows/shouts/spells on it until I know what its intentions are.