It's a perfectly normal trend and for a while PS360 will also have the best selling versions of popular series like Call of Duty and Assasin's Creed.
For example, Guitar Hero III: Legends of Rock, which was released in October 2007 (so almost a year after PS3/Wii) had the PS2 version outsell all the others. So I wouldn't be surprised if CoD 2014 sells better on the PS360 than on PS4/NextBox.
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