Christopher,
The plan is to have the J1.5 version out in early December. We're working through issues right now that have been uncovered in the J2.5 release and working on the v3.4.1 release. That release, we're hoping, will be available for J1.5 and J2.5.
As for benefits of extending your subscription, we'll be supporting the v4.3 release for quite a while. If there are issues that are uncovered, we will be making bug-fix releases and/or improvements as necessary and we've stated that will last through at least June of next year. So, you'd miss out on any bug-fixes or minor feature improvements. Beyond that, when your subscription expires, priority support in the forums and use of the Autotune configuration tool will go away. It's recommended to run Autotune every once in a while as Facebook adds new options and settings, and we keep Autotune up-to-date to make sure the settings are right for the version of JFBConnect you're using.
It's completely up to you if you feel those benefits are worth it. The returning user discount (~20%) is only available while youre subscription is still active though, so if you want to stay subscribed, it's best to do that before your subscription expires.
Best of luck with your site,
Alex