“For landscape stuff, apart from more MP, what’s the benefit of a different camera?”
More recent cameras will have much better high ISO capability, higher dynamic range and better RAW processing. The D7000, for example, will also have stuff like video capability vs the D60, and generally better features and technology all round. In theory, it will help to take better quality pictures.
Personally, I’d retire (sell) the 18-55 kit lens, and invest in some better quality lenses. Any advantages a new body will have, will be hampered by that basic lens. I’ve owned one and it’s really not great. It’s only real plus is that it’s small and light. Something like the 17-55 f2.8, 16-35mm f4 or 16-80mm f2.8-4 will be significantly better, if you want a zoom, but pretty expensive. Primes such as the 35mm f1.8 will offer significantly better picture quality. For landscapes, you’ll be wanting to look at a 16,18mm or 20mm prime, but again, expensive. For portraits, then the 50mm f1.8 is actually relatively inexpensive, and fantastic quality. With longer zooms, again you’ll find the cheaper ‘kit’ 55-200 type lenses being inferior to the much more expensive large-aperture stuff. But if you’re on a budget, then at least these will offer the ability to take pictures at all. Photography isn’t cheap once you start to get a bit more serious about it.
For now, concentrate on taking better pictures with what you have. Work out what you love about photography, and concentrate on that, rather than about equipment.