@Carolyn727 This is always a problematic situation. When you plan on selling, you really shouldn't have your calendar open to bookings more than a few weeks in advance, although I realize you may not have had selling in mind when you accepted these long-range bookings.
No, you can't transfer bookings to the new owner. Airbnb listings are non-transferable- you aren't selling an Airbnb business, you are only selling a house. A new owner will have to create a new listing and start from scratch.
Guests book in part based on the reviews and ratings earned by you. It would be really disrespectful to just transfer bookings to a new host, who may not run or maintain the place well.
You need to alert guests in plenty of time if it is in the market and give them an opportunity to cancel, with full refund, if they want to, or rebook with the new host/new listing.