They play both sides. Some of the heavies still believe the 7 days of 7,000 years each, meaning the earth is approximately 49,000 years old (they mention it in talks now and then). Others take the more rational view that the Watchtower magazine has stated that the creative days are of unknown length and could be (the appropriately vague) eons of time.
Never have they said what science knows: that the universe is around 14 billion years old and that our solar system is under 4 billion.