Eh I think you're underestimating the strength of marketing and exclusive content. On every major retailer site the XB1 version is ahead of the PS4 version. If we use Amazon as an example(since this is what most GAF users use with Destiny and the like), the standalone version of the game, bundle AND limited edition are all higher than the highest charting PS4 sku.
All marketing will note the exclusive content and promote the Xbox One version just as Sony has done with Destiny, so I think your kinda reaching with that statement... Destiny is still a system seller for the PS4 regardless of it being multiplat just like Advanced Warfare will be for Xbox One, period.