This is not encouraging but since it involves Wii third party support being embarassingly poor it's not unexpected. This happened with the Cube and the way things have been going, regardless of how idiotic it may seem, it was probably inevitable. Regardless of what the reason is third parties clearly do NOT want to support the Wii and it was only a matter of time before the console started losing some of the support it did have.
The Wii's sales will likely be unaffected. Nintendo will be unaffected. The Wii is so polarizing that it won't really affect the userbase; the Wii is either the absolute worst console or the absolute greatest and no one is going to change their opinion over this.
Will No More Heroes do better on the other consoles? Probably not. It's a big fish in a small pond and only stands out because for the Wii there is so little else for that target market. Though there is the image of the Wii being the casual console so Suda 51 probably believes that even if the overall Wii userbase is larger the amount of the userbase that would actually be the market for his game is greater on the other consoles. This is probably what the vast majority of third parties think (and we can't really disprove them though I don't think anyone has truly put up ANY sort of a decent effort and Nintendo's core games do sell).
According to the incredibly reliable source of Wikipedia,
when first day sales of No More Heroes in Japan were disappointing Suda51 said that "only Nintendo is doing well in regard to the Wii's success because of its adoption by casual gamers." He later retracted the comment but he did say it so at some point he probably believed it.
The thing is though is that No More Heroes isn't good enough to be a huge iconic game franchise in any environment. Low sales could entirely be deserved.