Which software are you using for the Jailbreak, Unc0ver or Checkra1n? If you're using Checkra1n, then yes, upgrading to 3.4.1 will still allow you to Jailbreak your device, but if you're using Unc0ver, you will need to move to Checkra1n.
I'm not sure if you can do an in-place upgrade or if you will need to restore the root FS beforehand. (Restoring the RootFS will remove the Jailbreak and all your tweaks).