As has already been posted on some other Steel Panthers related forums, it seems the guys over at 2by3Games are mentioning something called Steel Panthers IV. In the latest Developer Journal area of their website this was posted;
Here is the direct link 2by3Games and SP IV"Mike will continue to spend some time patching WitP, but will transition over the next few months to work primarily on Eastern Front. Keith will continue to be our technology guru, and will assist both Gary and Mike while they work on these two projects. He'll also invest some of his time to look into some new ideas that we have regarding a project which we all hope to get to in 2006 or 2007, Steel Panthers IV."