Well, I figure if we are to go to war in the future, we'll be forced to privatize the occupation in Iraq, handing the job over to private consortiums of manufacturers, oil comanies, and construction companies willing to foot the security bill in exchange for cheap labor and rights to the resources. The freed up troops would be used to similar incursions into other problem countries, with a similar answer to the problem of an over-extended fighting force: privatization.
edit: I think the future will see a decrease in the importance of the nation-state and a rise in the power of private fighting forces - more agile and capable of long term occupation and population management than a national fighting force, though I don't see national armies disappearing at all - just the opposite, actually. With the prospect of occupation becoming less of a concern, military expeditions will become much more lucrative.
