At this point, Florida and NC better be in play. I bet he'll put some money into TX too. Georgia wasn't a key state in the early stages of 2020 but it swung Biden's way.
You can't just "blue wall" yourself like Hillary and assume you have Michigan, Wisconsin, and Pennsylvania, you have to expand the possible opportunities for a winning map. In the later stages of the campaign they'll make the hard choices on where money and time will most effectively spent. For now, open the aperture as wide as plausible.