However there is the trend of "early access" games as well as games that continue to receive updates over time, minecraft or Wow would be examples of these, so there is a more gradual flow of sales.
It's not inconceivable that a game like minecraft could go on for 20 years , even if it's future form bares little resemblance to it's original release.
Of course this point is entirely theoretical at the moment since it will be many many decades before any video game ever created enters the public domain.
This trend, I believe, is partly in response to piracy. One might even argue that some derivative of this model (perhaps in conjunction with crowd-funding à la Kickstarter) could succeed even in the absence of copyright law altogether!
If you allow unlimited redistribution you remove much of that incentive.
I disagree. The vast majority of games developed today do not have a hope of paying for their own development, copyrighted or otherwise. It's only a very small proportion of games (so-called AAA) that are developed with the expectation of profit.
In particular, making a significant change to a work creates a new copyright for the changed work. If you boot up windows it will say something like "Copyright (C) Microsoft 1983-2013", meaning that the earliest code was written in 1983 and the last significant change was in 2013. That means that this version of Windows will enter the public domain in the year 2014+95. But you can start making copies of the original 1983 version of DOS already in 1983+95.
Personally, I would be mostly happy with current copyright, with an extension that items must be reregistered every 5 years, and available for sale. That would deal with the huge amount of items (games are a good example) where the original owners don't care enough to release the game as public domain, or often can't even be traced.
I would personally love to buy all video games made in 1993 on a set of discs sold by Microsoft for $5 that plays on an xbox.