The Zelda team(s) are workin', and never disappoint...
A great, epic DS game takes "only" 2 years of development, especially if it uses the same engine and the same control method as the previous game (PH), so it's quite normal to see the new DS episode first... and it will be great...
Now about the Wii one, it takes longer: it may need a new engine, maybe it will be cell-shaded, maybe it will be realistic à la TP, we don't know... it may need some experimentation with the wiimote and WM+, too... we don't know...
But i'm sure Aonuma and his team(s) are doin' the best they can to deliver another timeless classic, and chances are we will play it in 2010...
So no, no disappointment for me, the opposite i'd say: Spirit Tracks will be just fine, a perfect first course before the main one...
And btw, @OP: you shouldn't judge a game's quality on the first 2 minutes trailer you see... we know absolutely nothing about the "train" gameplay, we know nothing about the number of dungeons, the lenght and the scope of the game, etc... and visually, PH was wonderful, so... give the game a chance, and trust Aonuma & co: they are some of Nintendo's best, you should know by now...