As of 27 January 2019, 17 of the 19 national central banks in the euro area will no longer issue €500 banknotes. In order to ensure a smooth transition and for logistical reasons, the Deutsche Bundesbank and the Oesterreichische Nationalbank will continue issuing the notes until 26 April 2019 (inclusive).
Existing €500 banknotes will continue to be legal tender, so you can still use them as a means of payment and store of value (i.e. spend and save them). Similarly, banks, bureaux de change and other commercial parties can keep recirculating the existing €500 notes.
Like all denominations of euro banknotes, the €500 note will always retain its value and can be exchanged at a national central bank of the euro area at any time.