They'll metamorphasize into.. the same thing they are now.
Beastmaster wasn't hard before Abyssea.
I'm glad someone said it. People like to pretend it took a certain amazing skill bestowed only upon the chosen ones to play bst before abyssea.
Yeah, if you're good at the job it obviously makes a difference, but there is no difference when it comes to charming other than pre-abyssea will probably have charm sets already.
Even then, we'll see how that goes because jug pets still provide certain aspects that charmed pets cannot until we do more testing to verify otherwise (TH on dipper and falcorr, etc.).