Ah, I misread, sorry.
Anyway, went to AO3, and flynn/shaw is only the third most popular ship there with a little over 200 fics, of which like 70% of them are not explicit rating.
Number 1 is Wrathion/Anduin with over 550, Jaina/Sylvanas also over 500. (My favorite jaina/vereesa is only at like 37 RIP)
Khadgar/Lothar is about 150, khadgar/Medivh is also pretty popular, followed by Koltira/Thassarian. OCs are pretty popular but I don't feel like narrowing that down to f/f and m/m vs m/f.
Illidan and Kael'thas is also popular
So like if they were gonna go for the most popular ships, Wraithion and Anduin would be canon and Jaina and Sylvanas would have inexplicably hooked up.
ETA: if you go into the warcraft all media types tag which includes the movies, Khadgar/Lothar fics jump like 4x in number lmao