OmniOutliner 4.0 ... ?
 

In February of this year, we read this interview with Ken at MacStories.net:

"Don: Okay, fair enough. I also wanted to ask you about OmniOutliner 4.0. Is that still a focus at least for the first part of this year?

Ken: Not sure if it’ll be the [B]first part of the year or the second half of this year[/B], but it is certainly a big focus. The way we spread our engineering team around, the tasks we work on now, it has proportionally more than any of the other apps working on it. Actually, just since Macworld, I started feeling comfortable enough using it to edit my outlines… so that is a great milestone. It does have the new sidebar — we’re getting rid of the old drawer and folding it into a sidebar. The sidebar is present right now and you can navigate with it; the reimplementation is still very much in progress and it’s not ready for beta testing even. But the main outline is working and it is a good sign."

So I'm taking a wild guess it's not the first part of the year. Will it be the second half?

It could have been a focus for both halves of the year. He doesn't actually say anything about when he's going to [B]ship[/B] it :-)