One very simple way for video game developers and musicians and their respective companies can get a lot of money is if you take a game like, let's say LittleBigPlanet, and you let people upload their own levels to let other people download them.
But what they could do with these games is sell people songs (that may or may not be played only on that game, i.e. also put on the console for unlimited playback) and let them use these songs during the levels. One element that would probably make this a little popular or more popular is if the gamers were allowed to use certain songs at certain points, or even certain portions of songs at certain points in the game.
Something like this can be done for a lot of different games.
This would be replacing the soundtrack, if it even had any.
It costed about $250K to have a full song in a game back in 2005, which is why most games either feature songs that are re-made by another company or the songs are cut in half, but if the songs weren't put in the game, and were made available for download, game developers might be able to let us have full songs (at our dime) without being charged the full 250K. In order to do so, they would probably make a deal with the music companies that would probably have a minimum price paid to the music companies and would have a set amount of royalties per song sold.
The world of downloadable video game console content is going to go through a lot of changes in the next 10-20 years until it finds a stable point, kind of like what just happened with the internet. I.e., it doesn't have many new things that pop up every year.
Well, I think the price of games will drop to $50 by the end of 2008, and the microtransactions will make up more and more of the amount spent on games. I also think the price of microtransactions will drop, i.e. SingStar, Guitar Hero, Rock Band, Dance Dance Revolution, and all other song games that will (probably) have songs for download will see the prices drop to about $1 to $1.50 each. They currently cost a little more than $2 on Guitar Hero 2 for the Xbox 360.
And for those who say that portable consoles (the PSP and DS) will rule the industry by 2010, just shut your faces up!
The home consoles will always be in control, because most people who play games on home consoles don't buy handhelds (and that won't change much, either). And also, the game software for home consoles will always be larger than portables. The games/360 ratio is over 5 per 360 right now, and neither the PSP or DS has more than 4 games per console. (The PSP and DS were released before the 360 came out).