No offense to Bill Clark, but this posting makes absolutely no business sense. They shouldn't put plans on hold because there is a risk that a new edition will come out. If they did, they would paralyze themselves and never get anything new out. Might as well just close up shop now and be done. If I were at Necro, I would be thinking along these lines:
4e announcement will be made a minimum of 6 months before release, likely longer, so there is still time to get product out and sold. Keep trucking along in the meantime.
Continue to market to the 3.5 crowd. 4e will have early adopters, late adopters and people who never do. Make products good enough that people will want to convert them to 4e to be able to use them.
4e might be OGL, it might not. If it is, publishers will probably get some developer information prior to release to be able to get products moving and provide assistance in converting already developed but unreleased product. If it isn't OGL, either keep making 3.5 products, find another niche, or close up shop.