Not trying to take away from your comment, I think there's definitely a place for a "Wordpress for retail" and would be surprised if it doesn't exist (though it's not something I've really looked into). But I'm not sure something like that would easily scale to what Target would need.
BigCommerce, Shopify, Volusion are probably the closest to 'Wordpress for retail', but they seem to be mostly focused towards small businesses. Not that big businesses can't use them, but yea.
The companies you mention are all fine shopping cart providers, but someone who's selling more then a few products (not even the size of Target) needs much more then a simple shopping cart.
* Integration into their inventory systems and multiple warehouses. Do you want to be able to buy on the site, pickup in store? That means you need to tie your ecommerce site to your brick and mortar systems.
* Do you have vendors that dropship on your behalf? You need a way to import their catalog data and send them their orders. Did they mess up and not have inventory by the time your order arrives, better have a way for them to notify you, so you can notify customers.
* Gift cards that work online and in stores.
* Customer service systems that tie to your e-commerce so staff can help customers.
* Syncing all sales data to your finance, ERP, business intelligence and other back-end systems.
* Returns? A system for RMA, tracking returns, issuing refunds and exchanges. Want to buy online/return to store? better tie your store systems to your e-commerce again.
* Marketing? Have to tie your online store your e-mail software.
Building a full fledged e-commerce solution is much harder than many realize. There are great tools that solve parts of what retailers need but there is no all-in-one tool to get a large retailer online and just working out of the box.
There certainly is a "WordPress for retail" - you just have never heard of them because they're very good at marketing only to Big Brands... GSI Commerce (http://gsicommerce.com/)
GSI operates the ecommerce sites for Adidas, Calvin Klein, Marc Ecko, Levis, ToyRUs, RadioShack and many many more significant retailers (http://gsicommerce.com/clients/).
In addition to the e-commerce side of things they also look after warehouse and fulfillment which is why they also are able to setup and run Amazon Prime rival ShopRunner for the sites they maintain.
They're certainly "WordPress for retail" because if you look at most of the sites they run, they all look the same and have similar look/feel. It's all v cookie cutter - just set up the template, create an inventory, ship them the goods, and you're away.
Most interesting fact of all: EBay bought them in March for $2.2bn.
Oh wow that's pretty cool. I used to work on a lot of BigCommerce stores, and while they have an enterprise version which bigger companies can buy (http://www.interspire.com/customers/), I had never heard of GSI Commerce, who seems to have taken the cake for that market.
Not trying to take away from your comment, I think there's definitely a place for a "Wordpress for retail" and would be surprised if it doesn't exist (though it's not something I've really looked into). But I'm not sure something like that would easily scale to what Target would need.