Relax. This maybe the Zelda they were talking about, but there will definitely be another Zelda on the Wii.
If historic trends are any indication then there certainly will be:
NES: Two Zeldas
SNES: One Zelda
N64: Two Zeldas
GCN: One Zelda (spin-offs and collector's edition don't count)
Wii: Already one at launch, certainly another in the works?
Why not, look at portables too:
GB: One Zelda
GBC: Two Zeldas
GBA: One Zelda (remake doesn't count)
DS: Two Zeldas
Especially if Nintendo aims to have Wii around for longer than five years (which seems likely), there will be a second Zelda.