I would think if you chased them an gave them the good ol' foot-up-the-ass treatment, they would begin flying away again.
They are losing their fear of humans, because people just ignore them. Over generations, pigeons learned that we wont hurt them, but instead give
them food.
This is just a behavioral adaptaton to allow it to get more food.
I highly doubt that anytime soon they will begin attacking us and take over the world. When they start growing scales and/or teeth I will begin to get
concerned

. Untill then... I think were safe.