Although the Nintendo Wii U is set to outperform its predecessor in its first few months on sale, analysis from IHS Screen Digest suggests that the new console will have a "major challenge" in keeping this momentum up.IHS expects the Wii U, launching November 18, to sell more than 3.5 million units worldwide by the end of the year, compared to the 3.1 million units the original Wii sold over a similar sales period at the end of 2006.Though the Wii U's base price of $300 (a deluxe set is sold for $50 more) is higher than the Wii's $250 launch price, IHS said it expects Nintendo faithful -- the "evangelists" -- to drive high initial sell-through during the holidays.IHS senior principal analyst Piers Harding-Rolls believes that retailers will have a hard time keeping up with demand, with stock shortages expected due to Nintendo's tight inventory control.But looking to the future of the hardware, IHS notes that matching the original Wii's success will be a difficult task for Nintendo. "This time around, Wii U's pure innovation, coupled with a limited volume of high-quality Nintendo software, will not be enough to drive the ongoing sales momentum we witnessed with the Wii console, especially at a higher price point," predicted Harding-Rolls."Long-term success depends on ongoing consumer engagement delivered through 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 to go along with such innovation."The Wii U (and other platforms, for that matter) comes at a time when the market is highly-fragmented: Consumers have many options in how and where they buy and play their games. "Nintendo is still some way short of delivering a comprehensive engagement-led value proposition at the launch of the Wii U," said Harding-Rolls.