There's a huge opportunity for Shopify to launch a slick shopping service that puts a (much nicer looking) Amazon-style interface in front of all the various shops. Combine that with Etsy's marketplace and you'd really have a contender.
Independent aggregators are staging a minor comeback, thanks in part to the dismal failure of Google Shopping. I only ever buy PC components through PCPartPicker, I only buy games through IsThereAnyDeal. Third parties can offer real value in this space.
There isn't really a strong narrative that Google Shopping is any kind of threat to Amazon or Walmart. Nobody knows if it's going to catch momentum, or if Google will just kill in a few years.
Google can now dictate which webshop is shown first in search results on a product level.
I know retailers are sick of this. They need Google to be found on the web but they don't like how Google is destroying retail.