According to the developer's website, World of Goo is finished and will soon be sent to Nintendo for approval.
According to 2D Boy's website, development work on the much-anticipated World of Goo has been completed. In the same blog post, the two-man development team also state that they are "putting the final touches on the WiiWare version and expect to submit it to Nintendo for approval this month." They anticipate the WiiWare release will occur sometime before the PC retail release in November.