The marines are working a building another heavy helicopter, the CH-53K, but the first of these won't start arriving until 2014. So sometime in the next five years, the marines will begin experiencing an increased shortage of tactical airlift. Possible solutions include leasing of some other helicopter as some kind of substitute. Either that, or adjusting operations to include less helicopter support. That is not likely. The marines have already brought several retired (to the bone yard out west) CH-53s back to service. This involved refurbishment and upgrades, but there's no other way to get more CH-53s. Speeding up production of the MV-22 (currently at about one a month) is dicey, as this complex new aircraft is still expected to encounter unanticipated new problems as it enters service next year in Iraq.
The U.S. Marine Corps is in a tight race to get 360 MV-22 tilt-wing transports into service before their 150 fifty year old CH-53E helicopters fall apart. The MV-22 is meant to replace the CH-46E and CH-53E heavy helicopters. Four years ago, this seemed possible. But since the invasion of Iraq, some of those CH-53Es have been serving under harsh (hot and dusty) conditions in Iraq. Moreover, the service in Iraq involves more hours in the air than these helicopters would normally get. As a result, the marines expect to start losing about a dozen CH-53Es a year, too worn out for any further service, within the next five years.