“Multiclassing rule will follow closely the 5e DnD,” Vincke said. “On level up characters will be able to continue with their current class or choose a new class, provided they meet the requirements.”
So yes we will be able to to at some point. The focus now is (and probably should be) on making the classes work and feel good to play as they are. We most likely won't see it implemented until release or late in EA.
Found the reference...Final release is what matters with all features.
