CompTIA will release the NEW Security + SY0-501 on October 4, 2017. The new Security+ SY0-501 will replace the Security SY0-401 exam. The Security+ SY0-401 will retire in the english language in July of 2018 and will retire in Japanese and Portuguese in December of 2018. If you are studying for the SY0-401 you will need to test on or before the retirement date.
If you have a valid (un-expired) Security+ exam voucher it will be valid for either ONE of the exams once the new test is available.