Sony has revealed how you'll be able to buy Battlefield 4 on PS3 and upgrade to the PS4 version once it's released.
According to the post, inside specially marked physical copies of Battlefield 4 for PlayStation 3 there will be a voucher with a unique code printed on it. This code will allow you the one-time offer of buying a digital version of Battlefield 4 via the PlayStation Store for only £10.
We have also clarified this with EA via twitter who told us that you'll either be able to upgrade as above or upgrade via a digitally bought version of the game on PS3 to a digital version on PS4 for £10.
There was no mention of the Xbox 360 or Xbox One.