According to this GI story, Nintendo of Europe marketing boss Laurent Fischer has confirmed that a Wii storage solution is on the way - but it's not going to be a hard drive.
"We definitely detect that they [gamers] are serious and we know there is an issue in this, so it's something that we're working on," he said.
"Definitely there's no plan to issue hardware, an external hard drive, but we know that we have an issue in that area," he added. "It's very obvious and we're perfectly aware of it, but there's nothing we can say beyond this."
More through the link.