Incorrect, they will buy a body for the lenses and flash units they already have (even if it is only a few).
I disagree. The Rebel kit lens adds $50 to the price, and notice how Canon "updates" the 18-55 lens quite frequently (even though those updates are often insignificant as far as lens performance, it sounds new). The typical consumer doesn't buy an external flash (why? the camera has one!), and doesn't buy more lenses than came with the body.
But in fact, neither of us have data on buying habits of young or first-time dSLR buyers vs. people already owning other system components or other brands. But you know who does have those data? Canon, Nikon, Sony, etc., who collect that info, along with demographic data, salaries, occupations, etc., every time someone registers a new purchase. History has shown Canon to be quite adept at catering to their market.
Right now Canon are living off past glories, but unless they get off their backsides all their glory will be in the past.