There is the chance that more theaters may come online. Additional theaters need to be in the Fathom network (aka AMC, Cinemark, Regal). If you're looking to have a theater within the Fathom network join, your best bet is to make a request in the group sales page on their website:
If a theater is outside the Fathom family, they are always happy to talk to these locations about joining their network of theaters. However, if they only want to participate for The Chosen event, we will unfortunately not be able to honor that request.