They ought to put up a sticky in each of the forums, titled "why we don't announce our plans in advance" :)
The general scheme seems to be that they sit down with the feature request database, look at what has gotten the most requests, stir in their vision of where the product should go, make a short list of features, work on them until they are happy, then release it. The public gets in on the fun once there is something far enough along to send out as a "sneaky peek" for brave souls to use.
To get a request into the database, use Help->Send Feedback or send email to
omnifocus@omnigroup.com.