Learn Turkish: Sunum yapacak konuşmacılar yarın geliyor. - The speakers who will give a presentation are coming tomorrow.

In this sentence, yapacak is not the main verb. It is a future subject participle acting as an adjective. By placing yapacak right before the noun konuşmacılar (speakers), it creates a relative clause meaning 'the speakers who will make/give'.

Since the speakers are plural, why isn't it yapacaklar?

When you use the -(y)AcAk participle to describe the subject of the clause (the people who are doing the action), you do not add personal or plural suffixes to the participle. It stays in the base -(y)AcAk form, no matter how many people are doing it.

The event is happening yarın (tomorrow). Why is the main verb geliyor (is coming) instead of gelecek (will come)?

Just like in English where we can say 'they are coming tomorrow', Turkish frequently uses the present continuous tense (-Iyor) for scheduled or planned future events. Using gelecek would also be grammatically correct, but geliyor is very natural here.

The subject is konuşmacılar (speakers). Why isn't the verb plural (geliyorlar)?

In Turkish, when a plural human subject is explicitly stated in the sentence, it is extremely common and natural to leave the main verb in the singular form (geliyor). Adding -lar is optional but often dropped.