The last installment of Shinra Bansho Tenchi Shinmei no Shou, Volume 4, is coming next month. Pre-orders are live at places like AmiAmi.com right now.
It appears this volume will feature every main character from Shinra Bansho up to now (Saiga, Ryuga, Maxi, Kai, Sai, Ark, Apollo, and Moebius) – the exception, at least so far, being Fugaku from the single volume prequel Fugakuden.
In related news, a few months back, a character design contest was held where the winner would be featured as a “helper” summoned by Moebius in this, the last chapter (Thanks to Eis for the info). The results are in, and you can see the winner (as well as a few runners up) here.