Amen. Hyper (a gaming magazine) issue 204 had an article companing about this new marketing tactic - "Deaths to Salesmen". With one game people were bidding high prices for the store spefific preorder DLC on eBay after the games release, and then it was revealed they would all be released together in a DLC pack anyway anyway. It's quite a dirty tactic, I'd prefer they just stick to a collectors editon.
I find it pretty natural that they would release the pre order content as part of a dlc later.
It would often not be any legal way to get your hand on the pre order content after the game was released. Worst case would be to download a pirated version of the game with the pre-ordered content included.
I dislike pre order content pretty strongly as it’s a way to get people to buy a game before it has been reviewed, the game could be rushed or simply be bad. Yes the pre order content can also be bad, but you also have no way of knowing before you get it
Use a pre order rebate instead as pre orders is safe sales for the company so I understand why they want pre order sales. However to many companies use them and the pre order bonus items as a way to sell showelware before it has been reviewed.