When will humans out grow religion and belief in god?

[Mud]

What makes Satanism or Scientology a cult and not Christianity or Islam?

Because they are more mainstream?

Websters dictionary defines a cult like this:

1. formal religious veneration : worship

2. a system of religious beliefs and ritual; also : its body of adherents

All religions can be classified as cults, because that's what they are.

Exactly. It comes down to definitions.
If all organised mainstream religions died out and only Scientology was left, would there still be religion or not? They would say yes, but everyone else calls them a cult.
Like i said, in some form or another, 'religions' will always be around imo.