The Wii's internal memory has been a problem since day one. Gamers have been complaining that 512MB of space is not enough, and even more considering that the Wii's Operating System takes half of the memory.
At around 2000 blocks of internal memory, Nintendo is contradicting itself with the Virtual Console games and Wiiware, and is also making it hard on 3rd party developers who wish to have Downloadable Content.

Last week, Nintendo President Satoru Iwata said for its financial briefing for its FY08 results that they are aware that they must come out with the best possible solution concerning the Wii's internal memory.

"Statistically speaking, it is true that there are a small number of customers who feel that the flash memory is too small, while many others find that they have plenty of memory" adding, "However, because this small number of people are none other than the most avid players, we know we have to review the best possible solution to eliminate their inconvenience." - Iwata

Does this mean that we could possibly be seeing a HDD from Nintendo in the future? Or possibly an update to make USB HDDs compatible with the Wii?
Only time will tell.

Source: MAXCONSOLE - Nintendo Wii - Iwata says they will review lack of internal memory situation