I think the Icv2 data that shows D&D continuing to lead Pathfinder until the release of Essentials is consistent with the idea that new players retained by 4e at least made up for the loss of 3.5 hold-outs and those discouraged from trying D&D at all by the edition war.While 4e hardly seemed to be D&D at all to long-time D&Ders, it was more intuitive and easier to learn for new players coming to the TTRPG hobby 'cold' or cross-pollinating from the orders-of-magnitude-more-popular CCG and MMO hobbies. So, IMX, I did see significantly more new players retained by 4e and go on to become DMs fairly quickly. It was startling, really, because, I looked at 4e and saw a very complex game that had many systems you had to do a double-take and give a second or third chance before they made sense (much like 5e's neo-Vancian, actually, but /more/ of them). The thing is, that greater retention could never have been enough to make 4e a 'success' - certainly not in the sense of meeting the leaked revenue goals - because there was nothing in WotC's handling of the property to bring in /more/ new players to try it. Indeed, there was the edition war possibly dissuading some new players from trying D&D at all. Retaining more new players doesn't make much difference when the trickle of new players remains relatively slow. In 10 years, 4e might have built up an impressive base of new-to-TTRPG fans, but in only 2? Not a chance, even had it retained 100% of new players who tried it.
But why... why was it worth the risk of loosing all these supposed new players that had been gained as well as the hardcore fanbase of 4e... in order to get those lapsed fans back?
What risk? If there ever was a hardcore 4e fanbase as fanatical as the 3.5 and old-school hold-outs who rejected 4e, it would have already been lost by Essentials. Besides, even if the edition war were a strong indicator of loyalty, even the most brutal of 4vengers were still essentially(npi) defending 4e from attack, not holding it up as the only way to play the game. Finally, 4e fans have no 'clone' like Pathfinder or OSR games to flee to. So, WotC couldn't have seen much risk in alienating 4e fans by un-winding all the advancements made by 4e and presenting a 5e that fit more or less between AD&D and 3e in sophistication and quality. And, indeed, former 4vengers like myself are actively playing (well, running, in my case) and promoting 5e.