I think the word on the street might be that everyone will be given new cards. This means that you will inherit the new expiry date as per that card, which will mean Golds will get a year from that month to requalify.
Then again, some people are reckoning that as long as you have a card, that is as good as enough evidence and trumps almost any other information (e.g. putting your number in the system and it bringing up the status from the database). So some are intending to keep the old card and use it in the "spare year" if they don't requalify under the new regime, believing that lounge attendants will either (a) not really bother checking status after noting the details on the card (even if they write it down / take a copy), or (b) be compelled to accept the card, the status as printed and the relevant expiry date and thus grant entry.
It does make some sense that the card should be produced and should "override" any other indicator of status for the purposes of, say, granting entry to a lounge. It's quite conceivable that the *A central database can take at least a month or two to be updated, which can mean you may receive your card before the automatic systems print the correct status for you. Some lounges can be quite stubborn on insisting that a card be produced on entry, even if the boarding pass clearly indicates status and entitlement (a problem for those who qualify for *G whilst on travel). I suppose if A3 actually sent a memo that was broadcast alliance wide (sounds ambitious) that old cards were effectively void after a certain date (say early next year) so lounges would be aware to check for new A3 cards, then the technique described in (b) would also not work.