If Alien life was detected, it would have been hushed up to avoid global panic and mass suicides.
And all religions will realise that God/Allah/Budda/etc do not exist but have infact been worshipping aliens. Goa'uld System Lords (Ra, Apophis, Anubis) perhaps?
Explains the birth of Jesus...
Mary impregnated by aliens.
The 3 "Wise" men following the light of an alien ship which then shone it's searchlight onto the stable.
Jesus has "special" abilities, like heal people with a single touch. Alien psychic powers.