No One Knows Exactly What Would Happen If Mosquitoes Were to Disappear (theatlantic.com)

I would no longer be bit by mosquitoes and OFF! would probably go out of business.

If just the human biting species disappear that's probably a fair compromise.

Property values will certainly go up where mosquitoes had prevented enjoying an otherwise beautiful outdoors.

They are an important food source to birds, fish, reptiles and other insects. Getting rid of mosquitoes would be like getting rid of the plankton in the ocean.