MSNBC probably would have the easiest path to 16:9, but the Weather Channel would have a hard time because of their datacasting format and because the WeatherStar is mainly designed for 4:3 display, though you could argue that it's at near 16:9 already because of the bottom third graphic pushing up the screen.
CNBC though...that one's tougher. They have their CNBC HD+ feed and there's many places (health clubs and businesses and other public places that make up their daytime audience and will upgrade their TV's only when they die) that would actually object to having it forced to the HD+ design with that data because the screen would be nigh unreadable on a SDTV. Their studio shows are still all using 4:3 cameras, with the 16:9 pillars doubled on the empty right side for the HD+ data, so at this point (unless they've made BTS upgrades) there would be no picture to make widescreen if only the image without the HD+ graphics were used.