Generally speaking if you don't really want new features in new iOS, you should remain at your iOS 7.1.2, as newer firmware will eventually drag down iOS performance to a degree which, you may not want.
And now if you upgrade then you are buying a one-way ticket, no return.
Current iOS 9.3.3 jailbreak is semi-untethered jailbreak and it is bound to a certificate, which has an expiration date. IF, before next jailbreak becomes available, certificate is expired, what will happen? No one knows.
My conclusion is: be reluctant on upgrade, whether for jailbreak or not.