According to this map on the RATP website
https://www.ratp.fr/sites/default/files/inline-files/Carte-Vagues-Ticket+-8.pdf paper carnets are being withdrawn from sale at Metro stations in three phases, starting with phase 1 stations shown in blue from 14th October 2021, followed by phase 2 stations shown in orange from 13th October 2022 and, lastly, phase 3 stations shown in green during 2023 but with no exact date given for withdrawal. I would guess that it's a case of while stocks last.
At phase 1 and phase 2 stations, carnets ceased to be available from ticket vending machines from those dates but could still be bought from ticket offices until spring 2022. At phase 3 stations, the ticket offices already stopped selling them after that date so once the machines also stop selling them that'll be it.
The choice of which stations would fall into which phase of withdrawal of carnets seems somewhat arbitrary, although most major interchange stations seem to be phase 3.
Has anyone recently managed to buy a paper carnet from a machine at any of the phase 3 stations shown on that map, or from a Eurostar buffet car or one of the two Paris tourist offices at the Gare du Nord and the Hôtel de Ville on rue du Rivoli?
As of 1st Jan the price of single tickets have increased from €1.90 to €2.30.
Both the RATP and the Île-de-France Mobilités website give it as €2.10 as of 1st January 2023. I wonder if this means it was increased to €2.30 from that date but later reduced to €2.10. Or maybe it was originally planned to rise from €1.90 to €2.30 but was later capped at €2.10.