M.B.
First of all, I didn't co-sleep the entire time but that was out of fear of SIDS. He did start sleeping with us when he was a little older though. (about a year old) and then I kept him in a crib in our room until he was 2 1/2.
Don't let anyone tell you that you've done anything wrong!! You've given your son a strong sense of security and I have seen many kids whose parents were "tough lovers" and those who did some form of attachment parenting. As teenagers, those who started out close with their parents have stayed close and talk to their parents more than those that haven't. They have been less likely to get into trouble and less likely to rebel too. They're kids are very good, well adjusted, young adults. The tough lovers kids (that I know) have gotten poorer grades, have a lower self esteem (one of them cuts herself) and aren't very secure with themselves. You're not disappointing him at all, you're loving him and I praise you for it!
Now, my son had a bunk-bed and we created a "camping area" out of it and I told him he'd be camping tonight. (as I said, he was in his crib, in our room so he wasn't co-sleeping when we moved him but he was used to being in the room with us) I got a little toy lantern and set up "supplies" by his bed. (glass of water) and I put nature sounds on a sound machine outside.
I told him as a big boy, he was going to be camping out alone but if he needed us, we'd be in the next room.
He loved it and wanted to be in his "tent" every night.
If you have the room (which we didn't at the time) set up an actual 1 person tent in his room with a sleeping bag.
So basically, I'd show him that having his own room and own bed can be fun. It worked for us and it worked the very first night. :)
BTW, he's 12 now (12 1/2 actually) and he's very well adjusted, strong self esteem and in accelerated GT with good grades. :)