This year will mark the first holiday shopping season in decades without Toys R Us, the venerated toy store that shuttered after mounting financial problems and sliding sales. Amazon has already made steps toward filling the void, mailing glossy holiday toy catalogs — complete with QR codes for easy scanning — to millions of its customers in an effort to compete for shoppers that could go to Walmart, Target or other outlets for gifts. But don’t completely discount Toys R Us just yet: The brand, which decided in October not to liquidate all of its assets , has partnered with Kroger to put seasonal merchandise inside supermarkets in pop-up stores branded “ Geoffrey’s Toy Box .” Knowledge at Wharton invited two retail experts to discuss what the Christmas shopping season will be like without Toys R Us: Wharton marketing professor Barbara Kahn, author of the book The Shopping Revolution: How Successful Retailers Win Customers in an Era of Endless Disruption , and Mark A.…