Since the Disney Channel didn't start up until 1979, not much has changed at the studio during the 1970s. But as the timeline goes forward, Hanna-Barbera will probably falter ITTL, for a couple of reasons: most kids will be exposed to the higher quality of the cartoons Disney makes for television, and will then be turned off to H-B's objectively worse animation; a few of their popular shows of the 1980s (namely Pac-Man) won't be in their stable; and the Disney/Universal rivalry will spill into the world of animation in the 1980s, demanding insanely high standards as both juggernauts try to outdo each other. The company won't die or anything, but it won't really succeed during the period other than maybe one or two hits.
We'll see an update on them at some point, just not quite yet.