There is the very old adage that if it isn't broken don't fix it. There is no user interface that is simpler than of an ATM and does not even need Windows much less the 64-bit memory space of Windows 7/8.
Microsoft support is only meaningful if you have mission critical applications on tens of thousands of desktops running business software.
XP support was extended multiple times as corporate IT departments as a whole would not migrate to Vista which was flaky and required computer upgrades to compensate for its very poor performance.
With Microsoft playing games with Window 8 it is reasonable for the banks, and no companies are slower to adopt new technology than the banks, to see whether they will need to go from XP to Windows 7 or be forced by Microsoft to go to Windows 8.x.
I would expect that the ATM hardware will need to be replaced and banks if they are smart will instead go to Linux for their ATM's and migrate off Windows entirely. It would be the wisest decision for this application.
