Acording to IGN:

July 15, 2008 - Nintendo fans had expected the company to address two Wii hardware related issues at the Electronic Entertainment Expo 2008. Some kind of voice-chat solution. Check. And a proper response to gamers who have collectively run out of storage space on their system. That one, not so much. No USB hard drive. No official developer access to retrieve dynamic game data from SD cards. (At least, not for anybody outside of Vicarious Visions, making Guitar Hero: World Tour). And players themselves definitely don't have that kind of access.

But is a solution coming? And if so, when?

"There isn't anything that we can announce today, but we have been thinking along a variety of different lines regarding this matter for some time now," Shigeru Miyamoto told IGN. "So my hope is that sometime in the not too distant future we will be able to discuss some concrete solutions."

Exactly when that answer might arrive, we don't know. But at the very least, we're encouraged to hear that Nintendo hasn't simply chosen to altogether ignore the problem.

http://wii.ign.com/articles/890/890143p1.html

Whatever it is hope it comes sooner than later.....

simple. get memory cards.

Well, they are misinformed. SSBB also saves pictures and replays to the SD card, and I think that all games can read the SD card for things like this, but they just can't execute code off of the SD card or load Save Data.

Why not just release a USB hard drive?

they should just release a usb hard drive

I put my Wii in the freezer after downloading a bunch of games and whatnot. The cold air makes the files compact and it saves me more space.

Whatever it is, it will come with a pack in game.

The problem with a USB hdd is two-fold:

 - marketing perception:  it will appear to the uninformed that the USB hdd is required, making the Wii more expensive and complicated.  Uninformed consumers are a large part of the Wii market, which makes this a no-no.

 - encryption issues:  having encrypted software on removeable media could leave it for analysis on a PC to crack it, or possible slow the transfer if the encryption is especially thick (processor intensive). 

A possible solution I am thinking of has two parts:  store only the purchase key, with very strong encryption, on the Wii main storage.  Then optionally store the executable on either the Wii main memory or the SD card (or hey, the USB ports).  The Wii would know what software to look for automatically as all the purchase keys are on the main system, and the transfer could be quick as strong encryption would not be required; either the machine is allowed to run it or not.

The marketing perception roadblock would be minimized as long as all games can fit in a blank internal memory, and perhaps not documenting USB as an option even if it is supported.

Just my thoughts...