I am in a bit of a hurry, so will post properly later, but just to let you know:

1) Your bub is still so little. Do you even want him to sleep in a separate bed now? And I don't mean eventually, I mean right now - today - If not, then don't worry - there will come a time when he will want to sleep by himself. So enjoy those cuddles as they won't last forever...

2) DD co-slept and fed to sleep when she was younger. She is nearly 3 now and very very confident and falls asleep on her own, etc. Please refer to my point above - it may take two years for your DS to fall asleep by himself (DD went through phases before that, but it only after 2 that she consistently falls asleep without the boob, etc). It may take only a year, but regardless of the time - it will happen and it will be all over before you know it.

I believe that most kids learn to self settle naturally between the ages of 2-3, but some may take longer (hence the 4 year olds you mentioned), but they all learn eventually. Also, with the four year olds you're referring to - you don't know the full story - there may have been other medical/health/family issues at play, so please don't be quick to believe people who blame this on AP unless you know the full story.

Good luck.