Yeah - I think this is right. It wasn't that long ago that Disney were criticised for their choices, for sticking to animation and making another Princess movie (Princess and the Frog). They were always a big studio but they had a very specific market share, and now they're dominant.
WB is there legitimate competition though and have always been smart about nurturing properties - they've never had to deal with a really competitive force like Disney though. It wouldn't surprise me if we see Disney/WB play out like Marvel/DC comics over the next decade or so with those as the Big 2 dominating market share and other studios picking at the fringes.
Cinema does tend to run in cycles though - and I think it will be around the mid 2020s where we start to see other franchises and genres genuinely compete with the superhero/sci-fi milieu.
EDIT: In short, get all your superhero/sci-fi films out before then