The interesting thing is when it comes to 'ownership' of those shoppers.
Currently Tesco or Asda refer to 'their shoppers' as people who walk in to 'their' shops. However, the fascinating thing about an aggregator like echo is that suddenly those consumers no longer 'belong' to anyone but Amazon. Therefore, retailers may have to start working with Amazon / paying them to maintain their 'share of voice'. For example, we're already starting to see companies like Amazon selling branded placement opportunities on Alexa. If built in the right way (e.g. Alexa, what shall I have for dinner this week?' and delivered based upon solid data (e.g. purchase history, demographics, time of day and so on), there could be opportunities to deliver relevant content (e.g. a recipe recommendation) and a direct/immediate link to purchase.
There are still some things to watch out for with voice assisted shopping though.
As it stands the 'bots' don't always turn what they 'hear' in to accurate shopping lists and this could end up frustrating shoppers and ultimately losing trust. If the technology learns fast through the 'trialist enthusiasts' then we believe we will see a fast adoption to this by 2020.