I can tell you that individual replacement Wii U GamePad controllers will be available from Nintendo Consumer Service for a fee. In regard to warranty coverage for that accessory, at this time no specific announcements have been made. However, it’s worth noting that Nintendo warranties do not cover physical damage. - Owen Allen, Nintendo of America Inc.
Let's hope that the fee is $5 or less. I'd hate to think you'd be paying big bucks to replace a busted GamePad. Let's hope no one finds out the hard way! Thanks to Kevin for the heads up!