Metroid being delayed does not mean that Zelda was delayed. They are being made by different teams.
I have a feeling that the issue is with Metroid, rather than Zelda. Metroid either has had a teatable upended or the team is struggling to reach the deadline. At any rate, since a firm date was given (however unrealistic it may have been), the delay won't be for that long, since the team felt must have felt that they were on track.
The only thing that really worries me is the "TBD" release date. It's possible that Nintendo don't want to give any hints at all as to their Q3/Q4 release schedule, but the TBD makes me think it's possible for Metroid to even be pushed into Q4, which is worrying.
In the end, it's a wash. I still believe Zelda Wii will hit 2010.