It may be the beginning of a new trend, but the iPad is never, ever, going to kill print media. No matter how many iPads they sell, the population of iPad users will always be an exceedingly small fraction of the total audience available to print media.
Look how popular the Wii is, and yet there are only about 70 million sold. Even the 250 million iPods in the wild comprise a pretty small segment of the total print media audience. Of 6+ billion people on the planet, the amount who own iPods or Wiis is an awfully small number. Print media is not going anywhere.
Not to mention, you can't roll an iPad up and stuff it in your pocket or bag. If you drop an iPad on the ground it breaks, whereas if you drop a magazine you pick it up and keep reading. Businesses will not leave iPads lying around on the coffee table to read while you wait for your appointment, and you certainly aren't going to give your iPad to someone else when you're done reading your articles. As good as the iPad display might be, it will not be able to hold a candle to the picture quality and detail you can get in say an issue of National Geographic.
Besides, as electronics carry a heavy environmental cost to manufacture, e-media is not the environmental panacea many think it to be. I daresay that concerted efforts to increase the efficiency and adoption of recycling will ultimately be far more effective environmentally than any e-device in the near future will.
Ruahrc