Does anyone know when the new lens will be available? I'm thinking of buying the 16-35..
Well, these are theoretical lenses, so, it's impossible to say when it will be released. It might get announced before photo shows in April, it might wait til summer, it might never get released. The 5dIII "release date" rumors trace back to fall of 2010....so, anyone who waited based on that rumor waited a year and a half for the update.
If you need a wide-angle lens, go with the best available option now. If you don't need it, well, then you have the option to wait