Two years ago (October 2011) I submitted this idea to the first Shopify Fund ( http://www.shopify.com/fund ): "The second idea is to create a POS system that integrates fully into Shopify. Thus one can use Shopify to manage sales for all the store's inventory both those that one sells through the web and also those that one sells from the physical store. The POS front end for Shopify will allow for Shopify to expand…
I bet their customers have been asking for a way to synchronise their shop floor stock with their online stock, and Shopify would naturally want to be the provider of the whole experience.
There's probably many reasons why your idea never got picked up originally. They may have been already working on or thinking about it; it may be similar to another idea submitted; they may not have expected it to be a viable option at the time.
The fact they didn't even respond sucks as that's not a good community spirit. Just be pleased that you've managed to predict what the future was. The trick is how to do something useful with those predictions.