After saturating its target market of working class, bargain-hunting consumers, Wal-Mart is ratcheting up its low-price strategy to appeal to more upscale shoppers by expanding its merchandise lines to include organic foods, better wines, high-end consumer electronics and new fashion-oriented apparel. It’s an approach that carries some risk, say Wharton faculty and analysts, but that is dictated by intense competition and the lack of other opportunities for growth. The changes come as Wal-Mart — the world’s largest retailer with annual sales of more than $300 billion — has struggled with slowing growth and rocky transitions internationally as well as into urban areas of the northeastern United States. In a speech at the company’s annual meeting this month, Wal-Mart chief executive Lee Scott outlined elements of the strategy and quoted Wal-Mart founder Sam Walton: “You can’t just keep doing what works one time. Everything around you is always changing.…