I think the big challenge for NMH2 is the fact that unlike when it's predecesor arrived, the Wii shelves in stores are crammed full of games, including a lot more action games than NMH's had to deal with and those fabled long legs of RE4 are rarely seen anymore, at least not for this type of game. They tend to quickly drop down into the 5k/w range and quickly get pushed off store shelves by newer games.
Launched month and day against TvsC (which is advertised) sure doesn't help either, nor will Red Steel 2 and MH3 (they'll chop any legs out from under NMH2). From Suda's perspective this will still be a hit even if it doesn't sell as much as the original but I'm not expecting any great numbers from this. I would have expected at least 50k for first week considering sequels are more front loaded. Still a great game, enjoy it.