You can buy FIFA 15 when it hits the stores, in late September, but if you want to get your hands to the 15 Ultimate Team packs offer, you will need to pre-order it.
Since August 20th, 2014 it is possible to do it through PlayStation Network Store. You can choose between two editions: the Standard Edition is being sold by 69,99 Euros and the Ultimate Team Edition is being sold by 79,99 Euros. Quite expensive, no ? You will be able to download a few hours before the FIFA 15 release date of your PSN region.
If you want to pre-order FIFA 15 but pay less, you can try to do it through Amazon. If you are from UK, click on the following banner:
The PSN from Europe was the first one to make the FIFA 15 pre-order available.