this what its says on this page https://eu.finalfantasyxiv.com/lodes...ddd9615e3f659/

FINAL FANTASY XIV: Stormblood is scheduled to release in early summer 2017, at which time we will be ending service for the PlayStation®3. In preparation for this, players will have the option of upgrading to the PlayStation®4 version starting Monday, October 17, 2016 until Sunday, December 31, 2017.

it's the last month so its better do it in those 25 days that is left