>>713289670well that's good at least.
Not sure what being canon or non-canon means when the series is seemingly over. I don't expect an actual volume 5 given how long it took this to come out, and the general feel of it.
It's pretty obvious that she was setting up for a proper volume 5 with the ending of 4. Maybe the author just got too distracted with other projects, and decided to leave well enough alone until the demand got too high.