Totally depends on the cat.
OH and I took on two rescues a few years ago, they had been rescued as feral kittens but it had taken the sanctuary so long to find where mummy cat was hiding them that they were quite old by the time they were found and so totally unsocialised with humans.
As a result they have an inherant fear of people. They were rehomed to us in a dog cage, where for the first few weeks they hid in their litter tray whenever they saw/heard us (to the point where I had to give them a hidey hole in the cage as otherwise I could never clear out the tray!). You could see they were petrified and they stayed that way for months.
After a while they stopped hiding, so in the evenings we would leave the door open and very gradually they wandered round the living room. It was ages before we could take the cage down but eventually they were relaxed enough around us that we took it away.
To this day they are petrified of people that aren't either me or OH, one of them in particular is still not the best with us either, he needs a lot of patience.
When we got them we were living in a flat where they were totally indoor cats, but this is what they needed as they had to be socialised properly and also living near a busy road, it would only have taken for them to see a person before panicking and running in front of a car.
Now we live very rurally they do go out a bit, but only because they aren't likely to hurt themselves by running away from a person if they see one. One of them is still pretty much an indoor cat, he might pop out every now and then, but he just can't cope with it. He's a spesh :biggrin:
We also have two other cats who are super confident, you just couldn't keep them as indoor cats, they'd hate it!