Grocery stores won't be selling liquor or wine any cheaper than the liquor stores. That will be one line of products they can sell at a higher profit margin, which is probably what drove this decision. There are still plenty of liquor stores in states where liquor and wine can be sold at grocery and mini-marts/gas stations. There may be a few liquor stores hurt that are close to grocery stores, but, overall, liquor stores will do just fine.
Costco liquor prices are fantastic.