Developers have until December 14th to migrate away from OpenFeint, at which point it'll be offline forever. Even under normal circumstances this sort of deadline would be pretty crazy, but it's especially insane now given the massive influx of developers working around the clock to get their apps and games submitted before the cutoff to have them approved and on the App Store before the iTunes holiday freeze.GREE purchased OpenFeint for $104 million last year, perhaps a poorly thought out purchase with the service shutting down 18 months later. For newer games, Apple's GameCenter will enable most of the features that OpenFeint supported -- multiplayer support, leader boards, achievements and more.
Basically, to make this cutoff, developers are going to need to drop everything they're doing, open up every old project that utilizes OpenFeint and re-code all of those API hooks to either use Game Center or whatever proprietary solution they come up with on their own. Assuming that doesn't take too long, compiling, uploading, and crossing their respective fingers might result in no downtime for their users.
Pre-orders and previews underway ahead of launch.