You don’t say what zone you’re in, so I can’t advise you about when to transplant. I can tell you, though, that Baptisia has a very deep root system and doesn’t like to be moved – though you might succeed with a young plant. It would also require a large (deep) pot. The Buddleia would also require a fairly large container to balance what will become a large shrub.
Finally, if the soil in the pot freezes all the way through and stays frozen for any length of time, the plant will die. This is another reason for having big pots or for having a place to put them during the winter.