A post by Phoebus to the HereticII.com Forums gives the status of the Heretic II Enhancement Pack, which is finished and in Quality Assurance, hopefully to be made available soon. Here's the update:

We know the natives are getting restless, so we thought we'd give you a word of assurance. Right now, the EP is done. Jake (The Gent) Simpson has finished with the coding that I observed him working on first-hand yesterday. The EP has been turned over to QA for one, hopefully final session of bug inspection. But this won't be a week-long QA thing - although, obviously no one involved is about to release a buggy EP, which is why this process has gone on as long as it has. But as you can tell, things are wrapping up, and you should be playing the EP VERY soon now!