The card is itself the Annual Pass, although there only identifying information is the ID number, the aforementioned "PARKING" label, and a rough "valid" date range (in years - mine says "2013-2014", presumably ones now say "2014-2015"). No actual expiration date is on there, unless you write it. They have to be scanned to verify expiration.
The card is still necessary because there was no immediate plans to allow for scanning a MagicBand to validate for discounts. The card needed to be retained to show for the discounts, parking, etc.
As far as I know that hasn't changed. And as such, the card is mostly interchangable with the MagicBands within the parks for admission, FP+ redemption, etc. but not for room charges, room access, etc.
As for the question about the "combined" AP (Premier Passport), those are still separate cards (and I presume linked to the MagicBand as well). I haven't heard from anyone who has one yet to know what the full details are, but I heard that if you get it at WDW, you get an RFID card, but at DL you have to get it converted to one of theirs.
But I haven't heard of AP holders getting MagicBands yet (outside of the resort stay) - I haven't received anything about it yet. I may have missed a post though (incredibly busy weekend)