Obviously getting thinner and lighter is always the objective, but there are always some trade-offs (w/ having keyboard, user-replacable battery etc.).

The N900 is some 50g+ heavier than the iphones (133/135g) so one of next year's Maemo Nokia's (possibly without physical keyboard) might be expected to be thinner and lighter than those two, while still offering more features.

As a tablet guy I'd also welcome a thinner but especially a bit wider device, supposing there's a nice-sized edge-to-edge screen.

Only getting near 100g or below do I consider gadgets to be comfortably shirt-pocketable and it will be a while before phone-tablets with keyboard will get that light (or thin).