It’s hard, I know. I have 4 dc – 3 boys. We only have 3 bedrooms, too. The older 2 boys have pretty much always shared other than maybe the first yr because we also had exchange students of HS age, so they had the other bedroom. The youngest 2 shared until recently because it was really getting to be time for dd to have her own room. (That space is big enough we could have sectioned it off but there wouldn’t have been a window on his side. While not a biggie, it’s still something they need for ventilation. Anyway, I digress.) We now have all 3 boys in one room. ACK! Currently, they are 18, 16, and 10. If my oldest ds stays here, which he probably will, they will still have to share. The issues we deal w/ are most w/ the 2nd and 3rd ds, but the 1rst does add his own “thing” at times.
If they went to college they would have to share a room, so there still wouldn’t be any privacy. Issues would have to be dealt w/ in that situation, too. And, who knows what dynamics would be there. At least this way, they already know each other – and they’re family. If I remember, I think my boys went through a spell about that age of really getting on each other’s nerves. It has improved – some.
LOL 
If I had the space/money to do something different, then maybe, but it’s not going to be a reality here. And, honestly, I think I would rather them deal w/ each other than get into situations w/ roommates like I had at college.
Think of it another way – they really aren’t even going to be “home” for that much longer. We’re getting to that part of the parenting where they’re going to be leaving, much sooner than later.
One idea I had was to have the younger 2 boys share a room, giving the oldest his own room. But, I don’t know what the dynamics would be w/ that set-up. My other thought as I was typing here was to do what Miranda suggested. The boys’ suite would be more like they might do as young adults sharing an apt or other space.
K