User blog comment:Blueyoshi98/Pikmin 3?/@comment-117653-20100504164135

No details on the game are known yet, but (series creator) Shigeru Miyamoto has stated that the team is hard at work on the third game. We may or may not receive information this June during Nintendo's E3 press conference, but don't hold me on that. If it's being developed by Nintendo EAD 4 (which is likely), it may take a while for it to be released since they just wrapped up New Super Mario Bros. Wii. However, there's also the possibility (which is more likely) that there are multiple teams within the division, and when one team was working on NSMBW, another, more likely smaller team was starting development on Pikmin 3. After NSMBW's development ended, I'm sure some of the team members were brought over to work on Pikmin 3.

Note that this is all just me speculating. The only thing we know for sure is that it's being developed.