Regarding when and how alien life forms will walk among Homo Sapiens openly. This will never occur as expected, as the inhabitants of Earth have been led to believe by watching the movies. You are not alone now, nor have you been for many centuries. Your people's physical form will change gradually, such that you will be unaware of the change. Intelligence will increase, as will the use of telepathy. In some areas life forms not of the Earth will intermingle with the Earth's inhabitants, but these will be areas remote or involving few people. Word of these places will spread, just as word of the far continents of the world spread during the past millennium. Gossip serves a purpose in this respect. It allows for gradual acclimatization. In those places where many life forms intermingle, the people will be aware that they are among friends.
Introductions will be made during times of tribulation. The heart is most open when all seems lost. The mind is open to change when the world known before has been turned upside down. It is then that progress toward an open lifestyle will be most rapid.