As we got Ditto released not as our expectations (late for 5 months) and even Smeragle and Delibird are not yet released until now (with no news), I could just think of new possible non-legendary Pokemon to be released not as usual.
351:Castform ( 4 additional forms which require a weather system)
479: Rotom (can transform into 5 forms similar to electronic appliances)
745: Lycanroc (3 forms which the dusk forms cannot be received in normal ways)
746. Wishiwashi (change into its weak form when it is under 20% HP)