It is not really related to future tense, but take this sentence as example, how do you know it is "everybody will wait" and not "he will wait for everyone" ? Meanwhile in a sentence like "elma içer", can this be (theoretically) translated into "apple eats"?
I guess the bottom line is, how do you know for sure that there is or there isn't an omitted subject in a sentence?
Elma içer can indeed mean "the apple drinks." though a comma would be used after elma.
Herkes is different though. It has to be in the accusative case whenever it's the object. So "he will wait for everyone" would be: herkesİ bekleyecek.
Ah thx for letting me know the comma rule. So Elma doesn't have to turn into elmayı in order to be used as an object , but herkes has to be turned into herkesi, is this because Elma is a noun while herkes is a pronoun ?
Yes. Herkes can't be Indefinite. It's everyone, it englobes all. So it's always treated as a definite word. While elma can be elmayı if it is the apple.
Maybe I'm going to fast, but how would you say "Everybody is going to be waiting."?
We actually don't teach this verb tense in Turkish (and it isn't used very often to be honest).
"Herkes bekliyor olacak." :)
Can it also mean: everyone will be waiting? Which is more usual for such a sentence.
That would be "Herkes bekliyor olacak" :)
Everyone is going to wait is exactly same as everyone is waiting in English. What's the logic difference in Turkish?
They are not exactly the same in English or in Turkish. One is the future, the other is present continuous.
Fore some reason, it doesn't accept "everybody is to wait". Does anyone know why?
I am not English but I would understand your sentence more as an obligation than as future. I don't know if I am wrong but I would translate it to Herkes beklemeye lazim.