Seems like Developer 2D Boy have changed their minds, and Europeans will be graced with World of Goo on WiiWare after all.
Confirmed on 2Dboy's Official Website, the developer has realized that releasing the game to retail with extra content would be unfair to those who have to pay more and for those across the Atlantic that downloaded the original, so after Publisher talks they have decided to release it on Wiiware after all. It will be the same version as the US one, and it is not known what will happen to the extra content.
The game is set for a 1500 Wii Point price, and will be available sometime next month on both WiiWare and Steam (for 19.99). World of Goo has received review scores comparable to Super Mario Galaxy and is widely regarded as WiiWare's best game, so better look out for it!