"Everyone will get over the flu faster is they follow their doctors' instructions."
Millions of English speakers use the singular "they". It is not a new phenomenon of English. It has been used in the KJV, by Shakespeare, C.S. Lewis, and many other great writers over the centuries. Dr. Grudem has such a wide following of people who believe him. It is frustrating to hear him continue to repeat things which are simply not true of the English language. Too many people then simply repeat what he has said, because they respect him. But we should only repeat things which are true.
Here is the truth:
Generic "he", the pronoun Dr. Grudem wants used in English Bible, is syntactically masculine but has been historically gender-inclusive or gender-neutral, whichever term you prefer. It has a conflict of grammatical gender with semantic gender. Semantics always wins out when there is such a conflict because people communicate meaning when they speak or write. They do not communicate forms. Rather, they use forms as vehicles by which meaning is communicated.
Singular "they" is syntactically plural but semantically singular. It is understood and spoken by millions of English speakers. It has been spoken and written by English speakers since at least the late 1300s. There is nothing inferior about it, in spite of what prescriptive English teachers might say. It is neither worse nor better than the generic "he"--until we deal with connotative meaning and discover how people are impacted by generic "he" or singular "they." Language forms which are used by people are not good nor bad. They simply are, again, until we deal with the impact of connotative meanings.
Bibles need to be translated using the English forms that the majority of speakers in the intended target audience use.
Please, Dr. Grudem, we appreciate you and respect you. But please stop repeating what you say about the singular "they". It's not true and it is misleading many people, some of whom repeat what you say elsewhere such as on their blogs or from their pulpits.