It seems blizzard has been going cinematics crazy ever since the inception of Cata and MoP (Wrath Gate introduced us to our first ever in game cinematic but my point stands, they didnt really make a deal of it until making it mandatory in MoP).
Ever since, we've been getting progressivly more Cinematics than ever before, In WoD including trailers for patch content we got about 8-9 cinematics in total out of the overall experience (not) including the garrison upgrade cutscenes.
In Broken Shores and DH starter we already get introduced to about 5, begging me to wonder, how many more are there?
One thing I do suspect is that given after you finish the broken shores, the park district currently possesses a point you can fly on and there is no visible object there, im going to guess there will be a cinematic monument to Varian as they did with Vol'jin passing the Torch with Sylvanas.
We already have 1 additional patch content cinematic taking the number so far to 6, I predict, there will be maybe 13-14 by the end of Legion since blizzard seems fond of cinematics.
Im going to "not" include the broken shores mini cinematic when you arrive on the shore since it doesnt really count as a big cinematic much like Garrison upgrades.