If you are asking if that's true or not then the answer is yes, DOS isn't used in windows NT, 2000, or XP (or the soon to be released longhorn).
if you're asking if it's justifiable then the answer is also yes. DOS is great, but, it has security holes, and it cannot be made completely stable. There's also the issue of it's limited memory. DOS will always have it's place, but I think that the benefits of switching over far outweigh the drawbacks.