Does opening of emergency doors over wings, lead to automatic lowering of the aircraft's wings?
Wings are static.

The wings do not move in response to emergency door opening. There is no requirement regarding position of flaps, in most cases involving an emergency evacuation after landing, flaps are likely to be extended, but I don't think this is guaranteed.

Evacuation assistance

On commercial transport aircraft, there are marked routes on the wing for passengers and, if the exit point is more than 6ft from the ground, there are self-inflating slides that allow passengers to reach the ground.


Image from video by "Airline_Alex"



Evacuation on water

The inflated slides also work as life-rafts in the event that the aircraft comes to rest in water and has to be evacuated. Generally this applies only to slides at main exits, over-wing exits have slides that are not designed to be used in this way.

 US 1549



Regulations

The regulations in the USA say


  Each passenger-carrying landplane emergency exit (other than over-the-wing) that is more that 6 feet from the ground with the airplane on the ground and the landing gear extended must have an approved means to assist the occupants in descending to the ground. 


The manufacturer must demonstrate that they can evacuate all passengers and crew to the ground within 90 seconds using only half the emergency exits.

This applies to aircraft capable of carrying more than 44 passengers.



Variations in arrangements by aircraft

Not all aircraft need overwing exits and slides. Here are some B757 variants




From CRJ Resets

Boeing 737

As commenters have noted, the 737 does not have self-inflating slides for its over-wing exits.


Pessini

The 737 system does not always work very well


  Passengers climbed onto both wings, which
  were slippery due to the rain, but were able to see
  the markings indicating the direction of movement. It
  was difficult to see the ground in the dark and some
  passengers were not aware that they should slide down
  the flap surfaces. Others expected to find an escape
  slide. On the left wing, some passengers slid down
  onto the ground and assisted others. On the right
  wing, fewer people slid down to the ground, while
  others re‑entered the cabin and exited it using door
  escape slides when it was apparent that there were no
  visible signs of danger.


- from AAIB report