Since the goal is a 5DIII, I'd suggest a 5DII today. Start saving for the 5DIII, and consider the resale value of the 5DII as a down payment on said savings.
However, if you mostly shoot sports today or anything else that needs a high-performance camera more than you need the best in image quality, then get the 7D (but still plan on selling it once you've saved up enough to get the 5DIII).
Also, as EOBeav pointed out, if all you shoot is landscapes, there's really not that much difference between the 5DII and the 5DIII. Yes, the 5DIII is a better landscape camera, but probably not enough so that you'd notice in a side-by-side comparison of prints. Where the 5DIII shines is in performance (framerate, autofocus) and low light situations.
Think of the two of them having basically the same film low ISO film, but the 5DIII gets you a much better camera plus some higher ISO film. If all you want of a camera is a light-tight box with good film, the 5DII is the way to go. If you need more than just the film to get the shot, the 5DIII is the better choice.