Why "unfortunately"? It's only logical
That seems to be a bit of a non sequitur to me. I'm not suggesting that it's illogical, but that it is unfortunate.
I believe that if a significant chunk of people all wait to purchase a game 6 months or a year after it comes out, instead of when it comes out, it's going to make the game seem a failure, even if the total sales work out the same. And, obviously, people will be paying less for older or bargain-bin games and hurting sales figures that way.
I am as or more guilty of this than most. Because I could care less about playing a game when it comes out, I tend to, as I mentioned, wait until a game gets under $35 or even wait for $10 bargain bin deals. Every few months I raid a bargain bin and spend $80-100 picking up games I felt I wanted to play but didn't feel a strong need to support. _Unfortunately_ for the developers, my bargain bin purchase likely did little for the company.
And there's the long-held belief that quality RPGs, adventures, etc. sell better over the long-term, but I have no data to back that up so I'll leave that alone beyond this short mention.
So for certain games where I feel the developers did something special, I go ahead and buy it immediately, and get the special edition if I can (although I suspect special editions probably only benefit the publishers and not the developers, but that's just my uneducated guess). Bioshock is one of those special cases for me.