anandus
Errorist
An interesting article at Apolyton about the remnants of religions in Civ5 
And no, it are not leftovers from Civ4's xml's or anything.
Have a look
It looks like they really were planning on including it, but probably couldn't make it budget- or time-wise (I don't believe the "it doesn't fit the diplomacy'-excuse).
Utterly interesting. Maybe they'll include it eventually in an expansion?

And no, it are not leftovers from Civ4's xml's or anything.
Have a look

Very interesting indeed!Eight religions are named in the source files: Buddhism, Christianity, Hinduism, Islam, Polytheism, Shintoism, Spiritualism and Zoroastrianism.
[...]
After completing a shrine the game would tell you: "You have completed a majestic Shrine in CityName to honor ReligionName! You may now train Missionaries there to spread the faith." Other lines found in the language-files are, ao.: "By completing your empire's Shrine, you may now adopt a State Religion!", "An unmet Player has adopted a Religion!"
It looks like they really were planning on including it, but probably couldn't make it budget- or time-wise (I don't believe the "it doesn't fit the diplomacy'-excuse).
Utterly interesting. Maybe they'll include it eventually in an expansion?