it wont overflow, Since the ice, when it floats, displaces exactly its weight in water, when it melts, the water it melts into takes the same volume that the ice cube displaced in the water. So the water level should remain the same.
Assuming all the ice melted and the environment around said glass of water remains the same, then one would deduce that the water would be at a higher temperature than it was. Eventually the temperature of surrounding environment.