Well, the main question in my post was about the features. As mentioned, I didn't really see what improvements there are if you do not use
BlueIris directly but through a third party. Maybe I just read the wrong article/description of v4. I am rather willing to upgrade if there are any significant benefits.
As for the upgrades, there are many ways to do it. Some give no free upgrades even if a new version was released the next day. Others offer 1 month, 3 months or even live-time upgrades. Anyways, I just wanted to give some background info why I was asking about the expected release of v5. If you have any idea/guess then please let me know.