Yes. This happened to me just last week. I had purchased OAK-PHX tickets from the Fun Fares and Advance Purchase buckets the morning the schedule opened for Thanksgiving travel as those were the cheapest available seats. The evening of seven days out from the day of travel, 8+ seats on my flight became available in the Internet One-way bucket. They had not been available that morning, nor had anything cheaper been available prior to that since the original booking.