depends what youll shoot. landscape work doesnt require open apertures and pretty much any WA lens will do since you shoot at f/5.6-16
if its asap then go with the 18-35g for landscapes, anything else maybe the 16-35 will serve you better.
personally, im waiting to upgrade my Tamron 17-35 2.8-4 for the newly announced (though not yet for sale and no pricing as of yet) tamron 15-30 2.8 with VC. its going to be a killer lens. the tamron I have now is pretty much on par with the nikon 17-35 AFS, more or less.
I have a feeling the tamron 15-30 VC will best the legendary 14-24 AFS. my estimation is not before november at earliest and my guesss of pricing is in the $1000-1200. btw, sigma also announced a 14-24 f4 OS. but after seeing the tamron I lost complete interest.