In dreams about the theatre it will depend which part of the theatre is highlighted: if the stage, then a current aspect of our lives being drawn to our attention.
If it is the auditorium, then our ability to listen and understand the relevance is what is significant.
An open-air stage suggests communication with the masses rather than a selected audience.
A moving stage signifies the need to keep moving, even while performing a role.
The play we create in our dreams as an aspect of our lives is particularly relevant.
If we are not involved in the action, it indicates we are able to stand back and take an objective viewpoint.
If we are very involved it will be from an emotional perspective. You might also like to consult the entries for actor and audience.