I have completed remastering of Part III! It is being published as I type this. Note that I have changed its alternate title to "Chasing Ghosts". This is  to keep with the "ghosts" theme of the series and  because it turned out the original alt-title, "Chasing Shadows", is also the name of a map in the Cryptic mission "Skirmish", and I did not want people to confuse them.
Part IV will probably not require the kind of huge makeover Parts I-III got, just a bit more polish, and dialogue tweaks here and there to reflect the changes made in the first three installments.
Once all that's done, then yes, finally, I can start developing the long-awaited Part V in earnest! I hope to have it done sometime in October.
Last, but not least: At the request of my fleet, I have also begun creating a pair of companion missions (one space and one ground) to the series, designed for 5-player teams. I will try to get these done by November, then start work on the grand finale, Part VI.
paxfederatica is The Artist Formerly Known As NCC-89471.
"Ghosts of War" Parts I-VI [Fed] now available in the Foundry.
"Valley of the Shadow" Parts I-III [Rom] in development.