John Cena’s merchandise sales are way down from a year ago and WWE is nervous because Roman Reigns isn't clicking and the merchandise he is selling is coming nowhere close to making up the difference. Cena's always been kept babyface because of his strong merch, but WWE fears that as his audience is growing older, they're less interested in his merchandise and he's not doing nearly as well with the kids now as he was even just a year or two ago.
His recent merch was made in the same quantities they'd been making previous designs in, but with sales down, they're completely overstocked, which is the main reason they've been doing more post-holiday sales on WWEShop.com compared to prior years.
There doesn't really seem to be anyone on the roster that can fill the void. Cena is still the biggest merch seller, but his numbers have taken a big dent and the merch department is worried that if the Reigns coronation at Wrestlemania 32 doesn't go well, there's nobody in place to step up in terms of moving merch.