It is gradually being replaced by a new single-fare ticket in Île-de-France: the Ticket Métro-Train-RER, valid for one journey on all metro, train and RER networks, regardless of the distance travelled, excluding airport zones.

Origin-Destination tickets outside the Ile-de-France region will continue to be distributed, in single units only, at the stations concerned,
Origin - Destination ticket books are no longer sold, 
The price of an Origine - Destination ticket is now €2.50 (and €1.25 at the reduced fare), as is the  Métro-Train-RER Ticket.
If you still have any Origine - Destination tickets left, they are still valid and you can continue to use them.