Some kids who are forced to do things end up liking them. But a large number of kids will inherently hate it and shut out even the possibility of liking things, just out of spite and frustration. If the kids are actually afraid of being out there, you also run the risk of pushing them into their panic zone, where they are not learning or observing, because they are in fight or flight mode.

Is there something you could do that would introduce them to nature gradually? Maybe make it a short walk around a new park? Then step up to a little bit of hiking? Often, the trick with kids is to give them things in small, manageable doses and then quit while they are still having fun, so they look forward to the next time they get to do it.

It depends. If they're really not into nature and are going to be miserable, it's probably a waste of time. If they're the slightest bit interested they might really get into it. It depends on their personal interest. I would probably throw them out there and see what they get out of it. They might love it. They might hate it even more than they do now.

Sending them on a hiking trip is going to be difficult for them.... however taking them on a hiking trip may well be a different matter. If they can see that you're not asking them to do anything your not prepared to then it may work.

It doesn't have to be a 20 mile trek the first time. Just head off somewhere for a couple of hours I was taken on a few short walks with my parents an a hiking group when I was about 10 It wasn't far and we stopped for tea and a picnic. And I thoroughly enjoyed it (even though I was planning to hate every minute)

I'd probably say yes, but not all of a sudden.

You should slowly get them acquainted with Nature first, especially if they are not used to it right now. If there is an animal farm or zoo nearby, go biking to that place, and tell them some interesting facts about the animals there.
I myself like to check out http://www.kidzone.ws/animals/ for some interesting facts about animals, before I go to one of these with kids. There are tons of interesting things to tell.

With that, you might sparkle the interest of your kids in nature, now all you have to do is get them to like hiking. Mostly, this is a matter of 'Proof of the pudding is in the eating'. They need to experience it to possibly start enjoying it. Start with small hikes, maybe a couple of miles, and make sure they find an interest in it. Maybe give them a compass, and show them how to use it on a map of your immediate surroundings.

You could create a small hiking trip through town using that map. You could try to award some prizes if they are able to walk the 'city trail' all by themselves. This will surely increase the pleasure they have in hiking.

I hope this helps you along.