[UPDATE 2, 2:58PM:] Good news, everyone! GameStop Italy and our U.S.-based source have both said that this was all a glitch in the system and that Watch Dogs is—or will soon be—available for pre-order for Wii U again in Italy and the U.S. Apologies for making everyone nervous about this and for not getting that all sorted prior to publishing the first time.
First came the rumor of it happening in Italy, but it's happening in the U.S., too, according to a reliable Kotaku source: gaming chain GameStop is canceling pre-orders for the Wii U version of the anticipated, delayed, multi-platform Watch Dogs. That's not a good sign.