As you can read on Schan's excellent blog , 11.5.9 Premier Support ends by June 2008. This is almost tomorrow. There is no Extended Support offered, but Sustaining Support is there to stay.
By the way, Sustaining Support is not giving you any new updates.
So if you are on 11.5.9 with a localized payroll, you simply need these patches and fixes, due to statutory legislative changes. So Sustaining Support is not an option. So you have to upgrade to 11.5.10. By tomorrow.