While no one knows for sure what they'll do, retailers is not hard to phantom as the next target, they are already attacking link farms, panda focuses on on page seo issue, the one sector they really haven't targeted us online retailers. Additionally they started charging for better place in google stores search results.
Not sure what world you are living in, but they have been targeting online retailers for years. If you are not a big brand, you have been getting hammered in the SERPs since 2011.