Thanks to brickset.com for sharing the latest info related to Lego Trading Cards. It was reported that the mentioned trading cards was on shelves in UK Toys R Us yesterday!
At the moment we only know that there are 4 cards in every foil pack, priced at 50 pence. But it seems that the conditions of getting the foil pack are not really the same in other countries, it was reported that in Spain the packs are free with certain Lego purchase.
About the cards, there is a small number being printed on the top left corner and bottom right corner with at least 4 different colors border, looks like it is meant for some kind of game, example UNO type of playing cards game.
Have a look below: