This has being discussed before, but from current information the new i-Drive system is pretty different. How much of the system architecture has changed remains uknown right now. BMW are using a different supplier from the previous generation i-Drive.
At the very least, you would need a new screen, new controller, new center console (to house the new controller), new i-drive computer, new USB port (different from 6FL and used to import and save music files on hard drive), new telematics module to take advantage of new on-line services).
If the interfaces and wiring are the same, then perhaps its possible to upgrade, but I would imagine it would be pricey.
If the interfaces have changed, I would say it would be extremely tricky and alot of hassle. You would have to find away of getting the current systems (such as HD radio tuner, Satellite radio, or premium audio amplifiers) in your car to work with the new wiring and i-Drive system. You might just want to buy a new car, if you want it bad enough.
And as the poster commented above, BMW computers would need to be able to code it all to your car.