Learn Russian: Сначала подруги натанцуются, а потом наговорятся. - First the friends will dance to their hearts' content, and then they will have a good long chat.

This is the classic "satiation" pattern. By adding the prefix на- and the postfix -ся to an imperfective action verb (like танцевать - to dance, or говорить - to talk), you create a new verb that means "to do the action until you are completely full or satisfied." It emphasizes indulging in an activity until you simply don't need or want to do it anymore.

Why are these verbs translated as future tense ("will dance", "will chat") when they use present tense endings?

The на- ... -ся satiation pattern always creates a perfective verb. In Russian, when you conjugate a perfective verb using standard present-tense endings (like the -ют in натанцуются or -ят in наговорятся), the meaning automatically becomes future tense. There is no need for the future auxiliary verb будут.

Can verbs using this на- ... -ся satiation pattern take a direct object?

No, they are strictly intransitive. The addition of the -ся particle makes the action focus entirely on the subject's own internal state of satisfaction. You cannot use an accusative direct object with them. If you need to add details, you must use prepositions (for example, наговорятся о жизни - they will talk their fill about life).

Why does the sentence use а потом instead of for "and then"?