It will be a standalone mission (split over two maps), not 'part' of a mission. So it will be released in final form.
I'm not far from release now. Just got to build and script the final battle scene and finalise the rest of the level. Here are some screenshots:
https://i.ibb.co/Sn63fjZ/1.png
https://i.ibb.co/SJHdShL/2.png
https://i.ibb.co/zGfMSYq/3.png
https://i.ibb.co/3W6Xm2D/4.png
https://i.ibb.co/GQ34kP0/5.png