I pretty much agree, and I also would not be surprised to see Dumoulin or Despres get traded for a top young winger (I'm not expecting it to happen, just saying I won't be surprised).
That being said, I don't see Bortuzzo as a rookie. I see him as an everyday NHL player. Despres, he is somewhere between a rookie and 2nd year guy. That difference is due to consistency, age & experience. However, it does depend on a large degree on what's happening with the salary cap and other players, as to whether Dumoulin is part of this team next year. I know it's not ideal, but we are going to have to cut corners somewhere to become cap compliant. If we were able to sign Dupuis + Iginla + one or both of Cooke/Morrow, AND we're not going to make a change with Fleury in goal, then we may be in a situation where we have to insert quite a few young guys...
If the salary cap was not going down, my preference would be to keep Orpik. If we hadn't traded away two 1st round picks (Joe Morrow + this year's first) and two 2nd round picks (Murray trade), then I would be even more inclined to just keep Orpik through till UFA status and let him walk. I think, however, trading a guy like Orpik and/or Niskanen is essential in both creating cap space, but perhaps more importantly, to replenish assets & draft picks going forward. As I've said before as well, I also see us in a similar light as Chicago in 2010: we may have to dismantle a little bit, and that might mean we take a step backwards for a year or two, but we don't really have a better choice and it should make us a better team in the longer term.
If we move Orpik, I would like to retain Murray, just for that physical presence; and also because Orpik could garner a lot in a trade, whereas Murray won't garner anything (except for maybe a 7th rounder for his rights). Niskanen would also garner a decent return in a trade, but doesn't clear as much cap space as Orpik.
Bottom line: there's no perfect situation here, and although I think it would be less than ideal, I would be OK with putting all 3 of Despres/Bortuzzo/Dumoulin in the line-up. Most scouts felt Dumoulin could have stepped right into the NHL LAST season, and yet we played him as one of our top-2 guys in the AHL. Putting him into the line-up right away is not the same as putting in Maatta or Pouliot right away. And I wouldn't even rule out the possibility of Harrington as a dark horse to make the team over Dumoulin if he Harry out-performs Dumo in camp. Like I said: less than ideal, but I don't have a problem cutting a corner on the back-end and giving these guys the experience they will ultimately need to get to grow if it's because we're spending more money up front scoring goals.