Ha, thanks for the data . I more than anyone want 4.0 out the door, so don't see much harm in requests about it.
In general there are so many variables that account for when software is released that it is purely a game to predict; at least with Hype where we are more features/quality driven than schedule. But here's a small amount of insight...
For major versions 1.0, 2.0, 3.0, 4.0, we generally have them as paid upgrades in one form or another. As a user myself, I wouldn't find it savory to have too frequent of paid upgrades and also I'd like feature updates within to get value for the upgrade price. Based on this, the minimum I'm generally comfortable is releasing a major paid upgrade very 18 months. The basic plan was to do a .5 release 6 months in, and the next major release 12 months later. It doesn't always work out like that though! Recently we had the Hype Conference take up a bit of time, and some other business interruptions.
When we did v1.6, we found that even though it had lots of great features, it was pretty much ignored by the press. It was about the same amount of work as v1.5 (engineering, documentation, website updates, release-related support, etc.), but no real payoff and we were bummed. We decided not to do another .6 release. So why v3.6? I had fixed a lot of bugs for 4.0 and I wanted a release to get Export Scripts and a few other ad-tech features out sooner rather than later for business timing reasons (Chrome's removal of Flash, Edge Animate's demise). So you can think of v3.6 as half of 4.0 that users got for free . This also means it is likely 4.0 won't take as long. But hey, software never works out as expected, so I don't recommend holding your breath.