Ars Technica and their always informative retail mole leaked shipped copies of Patapon 2 would be a download voucher inside a UMD case. Sony later confirmed the rumor explaining the $20 retail game will also be available on the PlayStation Store on the same date for $15.
Last fall, Sony Computer Entertainment Japan introduced a similar strategy for first party games where downloadable versions would be simultaneously launched for a slightly lower price. The difference is retail versions of Loco Roco 2, Bleach: Soul Carnival, and Patapon 2 came with a physical UMD disc.