Yep, now multiclassing is confirmed we can make an educated guess that Jaheira will be a Fighter/Druid as she was in BG1/2
My question would be how they treat companion multiclassing - unlike BG1&2, when multiclassing was picked during character creation, in 5e multiclassing happens on a level up. As such, unless our control over companions class progression is limited, Jaheria can ship as Druid or fighter only.
I don’t think I would want to be forced to have Jaheira as Druid/fighter, as a I would rather keep an ability to multiclass companions as a I wish for subsequent playthrough, which I think will be needed considering fairly smal pool of companions.