It is possible for users to exist in multiple stages and receive more than one email in a day, but not a usual occurrence since the platform is selecting the stage and template that it thinks will convert the best.
If this were to occur it would only be for the following scenarios:
It's their birthday so they receive their Birthday stage email.
They reside in the Ready to Buy stage so they receive their Ready to Buy email.
They abandon an item in their shopping cart and receive the Cart Abandon stage email.
It's their anniversary so they receive their Anniversary stage email.
They reside in the At-Risk of Leaving stage so they receive an At Risk email.
They browse abandon and receive their Browse Abandon stage email.