Talkiet: You can't go wrong with either, but I would caution against investing in a brand other than Nikon or Canon if you think you might ever want to grow the system - Sony, Olympus etc produce some decent cameras, but they don't have the same range of lenses or accessories, and generally they aren't quite up with the big boys.
I would think that very few non-professional users would ever want more than a standard zoom, telephoto zoom, fast normal, and macro. These should all be available for any established camera system. In fact that majority of people who own interchangeable lens cameras probably don't even go beyond the lenses that were supplied with their cameras.
I agree that it pays to think ahead, and specialist lenses will undoubtedly be important to some people, but it's important to remember that there would be very few people who would invest many thousands of dollars on photographic equipment for casual use.