Well, "confirmed snacks" are confirmed by the DISers who've actually been able to obtain them using a snack credit - so by definition, there can't be any 2009 confirmed snacks until, well, 2009.
Most likely, the same items that can be purchased with snack credits in 2008 will be valid in 2009 as well. But the only guaranteed snacks are the "for example" ones described in the 2009 brochures - including, but not limited to (because I'm working from memory, not looking at the pdf) 20 ounce bottle of soda or water, medium fountain drink, 12 ounce coffee or tea, single-serve bag of chips/Doritos, ice cream novelty, single-scoop box of popcorn...