If it were possible for the iPad to own 138% of the tablet market it probably would, but competing devices have already launched like the Motorola Xoom, are about to launch like the BlackBerry Playbook, or will be launching later in the year like the HP TouchPad and more Android Honeycomb tablets.
Some will be smaller, with 7 or 8-inch screens. Some will be slightly bigger with 10.1-inch screens. Most will have Adobe Flash support to varying degrees. They'll have more ports (and not require camera kits or AV adapter dongles). They'll have webOS card view (even if they come from RIM) or a more desktop style UI. They won't have iOS apps but they'll have Android apps (even if they come from RIM) or webOS apps. They may have really fast LTE connections at some point. They won't have iTunes but they probably will have wider native support for video and audio file formats. Even 3D. They may or may not be easier to hack.
But they'll be different, in small or big ways. And for many people they'll be not-Apple and that will be tempting.
Will it tempt you? Be honest now -- let me know why! (or why not!)