There won't be wii HD, Wii upgrade of any kind shot down be Reggie himself according to wii.nintendolife.
heres the link businessweek.com
Wii will prevail
Be it an upgrade to the existing hardware or a brand new console, there have been many rumours and forum chit-chat over the last year concerning Nintendo’s plan to release a successor to the Wii.
However, Reggie Fils-Aime has confirmed the continued support to current hardware in an interview with Bloomberg Business Week.
Reggie has gone on record to say that no announcement will be made regarding any new hardware at the upcoming Games Developers Conference and that the Wii has a very long life in front of it.
Many analysts believe that rival companies plans to step into the motion control market with higher specification consoles and a slowdown in sales of the Wii will drive Nintendo to release a new console.
But with new games based on fan-favourite characters due out this year in Super Mario Galaxy 2 and Metroid: Other M, Nintendo is confident that any downturn in hardware sales will be reversed and the Wii will continue to be a console that dominates the living room and sales.