Learn Spanish (Latin America): A lo mejor el mago hace otro truco.

You are right that words expressing doubt, like tal vez or quizás, usually trigger the subjunctive mood. However, a lo mejor is a special exception! It is almost always followed by the indicative. That is why we use the regular present tense hace here instead of the subjunctive haga.

Why doesn't it say un otro truco for "another trick"?

In Spanish, the word otro already means "another" or "other" all by itself. English speakers often try to translate "another" literally by adding un or una, but you should never say un otro. You just put otro directly in front of the noun.

Could hace be translated as "will do" here?

Exactly! In Spanish, the present tense is often used to talk about things that are about to happen in the near future. While it literally translates to "does," saying "Maybe the magician will do another trick" is a completely natural way to understand this sentence in English.