I would hazard a guess that the 600-EX-RT has far outsold any previous top level flash since the 550EX because it introduced a truly new and innovative feature. I am in the process of selling my last 550EX's, I never saw any practical advantage to the 580EX/II, and have replaced them all with 600's. I don't care about 460-EX-RT's, I don't care about monolights (though I know some do), I suspect Canon are more interested in my speedlite opinion than yours because I am a purchaser, you are not. I don't care if they don't do anything else with the RT system for another ten years, the 550's lasted me that, I bought it for what it can do, not refuse to to buy it because of what I think it could do.
that's all fine and dandy. It would have still been in Canon's better interest to push the RT system out as vehemently and quickly as possibly. You could still have purchased any number 600EX-RTs at any given price. No damage done. And in addition other pros and amatuers would have purchased millions of 450EX-RTs and RT-tranceivers Millions of them. And the Canon RT wireless ETTTl-System would be ubiquitzuos throughout the Canon-ecosystem by now. More "tie-in" of existing customers (in addition to invstments in glass) and mor lure for potential new customers. Much larger and longer-lasting comparative advantage against competitors without radio-wireless ETTL-system. Win-Win-Win.
Under almost any market condition, if a company sells 2 or 3 "similar" products they will sell more in TOTAL compared to selling 1 product only. Even Canon does not only sell 1D-X. And 4 versions of white 70-200 lenses. Same applies to speedlites. :-)