Multiple controller support has been a much speculated about issue since the announce of the Wii U console at E3. After Miyamoto said they were focusing on single controller only, many thought that was the final answer. However, Nintendo CEO, Iwata, has spoken up with:
“Technically, it is possible for the Wii U to support multiple Wii U controllers.”
However, due to the high price of the Wii U controller/console, the focus will primarily be on single controller games.