So it seems that it is a 12 month extension on the expiry date on your current card as shown up to today.
This benefits those who have qualified and upgraded in their current year: the card naturally is valid until the end of the tier point year after qualification. They will therefore get an additional 12 months.
This does not benefit those who have re-qualified in their current year: the card expiry is not extended until the end of their current TP year, so this will merely duplicate what the extension will do anyway (it is possible BA IT will do something to correct this anomaly, but currently I have heard no plans)