Wal-Mart Stores Inc. (NYSE: WMT) has been the leader in DVD sales in the U.S. for years now. It's estimated that 40% of all U.S. DVD sales originate within the doors of the world's largest retailer. But, could those days be coming to an end?

With Blu-ray DVD players coming with built-in internet video streaming, cable and satellite having video-on-demand choices of all recent movies, and more people buying content from Apple Inc.'s (NASDAQ: AAPL) iTunes every day, what is the future of the physical DVD?

With Wal-Mart responsible for about 40% of the DVDs sold in the U.S. it probably sends shivers down the spines of movie studio execs whenever the global retailer makes any kind of move that could upset the balance of DVD sales. These sales have been an ever-increasing part of the planned profit margin built into movie production budgets. With Amazon.com and Apple Computer, Inc. (NASDAQ: AAPL) recently launching online full-length movie download services, the question has come up again and again on whether online alternatives will dent physical DVD sales. With Wal-Mart cornering the market here, that is the retailer's laser-focus right now.

To turn this discussion upside-down, what if Wal-Mart was to join the party and offer downloadable full-length movies itself while still selling physical DVDs at its stores? Would Apple feel the heat? Sure it would. But right now it is Apple that may be putting the pressure on the industry. Tens of millions of iPods may need all this movie content soon, and movie studios would be unwise not to try and capitalize on Apple's hardware success by licensing movies to be downloaded from Apple's iTunes music and media store.

With iTunes movie downloads going for $14.99 each at this time it's easy to see why Wal-Mart would possibly enter the space, although the hardware and software details would be an interesting mix of jumbled acronyms to watch. I'm not sure I've seen a DVD at Wal-Mart for more than $15 when I've looked, and the retailer would probably feature movie downloads for less than $12 in my opinion, like an $11.99 price point. After all, isn't Wal-Mart supposed to have low prices, always? Could Wal-Mart succeed here? If you hold WMT shares, what do you think?