Michael Pachter, analyst for Wedbush Morgan, isn't freaking out, and he wants you to know that you shouldn't be either. He notes, while speaking on the subject of March NPD numbers, that even though the month saw hardware sales numbers drop across the board, that really has more to do with extraordinary sales for all comparable months. Speaking with GameSpot, Pachter said, "It's entirely possible that we were just up against an impossible comparison ... we're looking at a comparison to Grand Theft Auto IV in April, so it's likely that April will be down as well," referring to the release of Super Smash Bros. Brawl in March of 2008 and the subsequent month's GTAIV.
What he does find worrisome, however, is declining Wii software sales after a year of strong console sales, reportedly doubling the system's installed-base. "Given that the installed base of Wii consoles has doubled in the past year, we find it remarkable (and somewhat disconcerting) that Wii software sales were actually down year-over-year in March, dropping by $72 million, or 26 percent." Pachter doesn't see the future as grim though, pointing out that this summer's release of Wii MotionPlus and Wii Sports Resort should put some wind back in Nintendo's
Source 1 - GameDaily
Source 2 - GameSpot