A research report from IHS Screen Digest is predicting that three to five million Wii U consoles are likely to be sold by the end of this year, beating the Wii's 2006 numbers. The report attributes these strong sales to demand from "Nintendo evangelists," including many who first came to console gaming through the Wii. The high demand is likely to create shortages during the holiday season.
In the long term, IHS does not expect the Wii U to match the Wii's sales numbers, suggesting Nintendo will be unable to deliver "the constant release of high-quality content from both first and third parties, a competitive non-games entertainment proposition and a sound digital and online strategy" needed to reach Wii-sized sales figures.
Of course, this is just an educated guess on the part of IHS, but few people expect the Wii U to sell as well as the Wii, which took the world by storm. But then, few people predicted the Wii would sell as well as it did, so Nintendo may surprise us all.