it's not uncommon to have things to put up for sale and not do so. Look at, for example, a model site such as ChristinaModel.com. They may shoot a few months of updates all in the space of a few days. And then they just stretch it out over that time and don't have to worry about a photoshoot for a while.
In Lorekeep's case, though, if the comic is still enjoying fair and strong sales, then it makes sense to hold off on the video to keep from cutting into those sales, and possibly picking up a few additional sales of the comic once the video is offered, in case people missed the comic when it was first posted.
Just saying, he has a strong and logical reason to not be putting it up just yet
