A) Goodra (probably) is able to defeat Bisharp because of a move-ability combo: Rain Dance, which activiates Hydration. Hydration will prevent Goodra from becoming paralyzed.
B) In addition, it is almost near impossible that the writers are actually going to have Goodra beat Charizard, who based on both images and the preview itself, will become Mega Charizard X in order to battle Ash-Greninja.
However, Charizard is scene flying through the rain which could provide Goodra with a chance to weaken Charizard for Greninja's turn. In addition, should Charizard Mega Evolve
before battling Greninja, any of Goodra's Dragon-Type moves will be super-effective.
OF COURSE... This is all just in theory... Anything can happen (though again, I very much doubt that Goodra will beat Charizard
)
Anyway, thank you for listening to my little rant