New ticket machines have now been installed at Gunnersbury and Kew Gardens. They offer tickets to all National Rail stations (I tried Penzance and Wick), and tickets starting from other stations. The menu also had a grayed out button for ticket collection, and Oyster Travel card extensions outside the zones just led to a blank screen.
At the moment, the ticket offices at Kew Gardens and Gunnersbury seem to be open. No sign of any change at the Bakerloo stations.