No. it's not the future. We indicate the formal by putting everything but the noun in the plural. E.g. '"मेरे दादा खाना खाते हैं" which would mean "my grandfather eats food." You'll notice "मेरे," "खाते," and "हैं" are all in the plural even though "दादा" is singular. This is showing respect to the grandfather (showing respect because he's older.) In the same sense, we use आयेंगी (plural) to show respect to someone of seniority.