Intersecting threads

As my faithful readers know, I interweave almost all of my tales. With the current stage of 'Mates', coupled with the 'Prequel' in 'Black and White', there is an unfinished story there, of Neil and Maddy.

Obviously, I know where that story goes. I am considering fleshing it out, as I did in 'Black and White', but it comes after all the stuff I have already written. I think it might work as a standalone, even so. What do people think? Should I write and post it now, or leave it till after 'Mates' has run its course?