And who says OS X multitasking will be exactly like iOS multitasking? I’m sure on a desktop OS, it’d be perfectly acceptable for an app to request a background task of infinite length, as opposed to the 10 minute limit on iOS. They can already defer sleep, so why not?
If the past is any indication, they’ll require apps be rebuilt with a new version of Xcode to take advantage of this new multitasking scheme. Apps as they stand now are completely incapable of dealing with this kind of functionality, and it would break too much stuff to reasonably enforce right away. I’m thinking it’ll be an App Store requirement, not something enforced at an OS level. In any case, I’m looking forward to better power management.