As a landscape photographer I'm kind of obsessed with sharpness. Most of the time there are of course other factors limiting sharpness but I don't like the lens to be too much of a limiting factor when the other conditions are good.
I'd like to see a 24-70/2,8 IS. The current non-IS is really sharp, but with IS it would be a better all-around lens. As it seems we will get a new 24-70, but perhaps without IS and I don't think it is likely that a new lens can be considerably sharper than the old... we'll see.
Then I'd like to see upgrade of the lower cost 35mm and 24mm, those lenses are not really that sharp. I think primes should outperform zooms in sharpness, but the 24-70 is actually somewhat sharper than those at f/8. The L-lenses at 35 and 24 are slightly sharper than the zoom, but really expensive and somewhat heavy - not a great buy (for an amateur that doesn't need the superior build quality) if you intend to shoot at around f/8 most of the time.
The tilt-shift TS-E 24mm II is a great lens, if you're serious about landscapes and have the money - it is one to own. The old 90mm TS-E performs really well too, but the 45mm is not performing so well on a modern high megapixel body, so a new TS-E 45mm would be great. Actually I think TS-E at 35mm would be more useful than 45mm though.