Chances of anything like this being actually implemented are about as close to zero as you can get (IMHO), but this iOS 6 Interface Concept video shows some pretty awesome ideas about how iOS multitasking and UI can be improved.
I really doubt that Apple would move to something where there are so many issues around discoverability, compared to the simplicity of “tap icon, app starts” that they have currently. Guess anything is possible though :)