This is one of the questions I kind of dread answering! I think most people already have their opinion on co-sleeping, and judge my answer based on what they have determined is best for their situation.
Are we going to co-sleep? Quite possibly. We are going to do whatever is best for H.
Yes, H will be about 18 months old when we meet him and he may very well sleep in our bed or in our room for a long time. Yes - we may sleep (or try to....not saying we'd actually get much sleep) with an 18 month old in.our.bed. Ridiculous, you say? Maybe for your situation, but not for ours.
H will have spent the first 17+ months of his life in an orphanage. With multiple caregivers. With many children. He most likely does not know what it's like to have someone respond to his every cry. To hold him when he's sick. To gaze into his eyes when he's being fed. To meet his needs, each.and.every.one, quickly.
We will, in many ways, be starting from scratch with him. Which includes having him super duper close to us at all times, even in the night - just as you would a newborn - so that we can respond to him as soon as is humanly possible.
We're spoiling him? Nope. No one (in their right mind) would say that you're spoiling a newborn if, in the middle of the night, you respond to their cries. It's just the way things are supposed to be. It's normal. We're not spoiling him but teaching him that we will meet his needs, whatever his need is and w-h-e-n-e-v-e-r he has a need. He's never had a chance to learn this, and we are the individuals, blessed, if you ask me, who get to be there for him. Immediately. Even in the middle of the night....even for just a whimper.
It's what's best for him. Not forever, but for a time.
The same goes for a number of other things - feeding and discipline and other stuff. If you have only biological children, you may think we're nuts. But we're not nuts - we've just read books and gone to trainings and talked to other parents who've been there/done that. We're acting based on proven data. We're doing what's best for our son. What's best in our situation :)