First of all why is everyone waiting? The Ody's are on the lots here. The dealer on the Ohio/PA border here has a Granite Green EX that he will sell for $400 under MSRP. Also he has a few LX's and maybe even an EX-L.
To answer your other question, I have no idea about th '03 Sienna. I sure hope they give it more HP and more room though... it's kinda cozy in my opinion.
(If you want the GG EX I bet the dealer would pick you up at the Youngstown OH airport...)
I would avoid buying a redesigned model of ANY car (i.e. a 2003 Sienna) for one or two model years. This gives the manufacturer time to iron out the wrinkles and refine the design.
With modern computer aided design and manufacturing techniques, this isn't quite the issue that it once was. Nonetheless, let other buyers be the guinea pigs. Toyota doesn't want to lose any 2002 Sienna sales so I don't think they'll be in a hury to unleash the 2003 model.
Buy a proven design now. If you like the new Sienna when it arrives, trade-in for one in 2005.