It's clear to me that WotC knows that fully merging the two IPs' lore would alienate a certain number of fans on both sides. Obviously, they can make some money by doing so, too—probably much more than whatever they might lose by alienating fans who have an investment in the existing lore. WotC has announced that they're considering doing the lore-merger. Part of the motive for the most recent D&D survey, I believe, is to gauge how receptive D&D players would be to that possibility.
The fact that when I entered my age, that survey abruptly ended (rather than continuing on to the final section, which was apparently aimed only at younger players) probably provides me with all the tea leaves I really need to read. Edit: Apparently age may not be the reason the survey ended early for me and others.