I just noticed that the latest version of Nemo in the Ubuntu repo (both Disco & Eoan) is version 3.8.5.
Nemo is maintained by the Debian Cinnamon team. So uplifting the version of Nemo for that mean means a stack upgrade for the whole of cinnamon.
Since Debian is in freeze state any upgrades will have to wait until Debian buster is released.
From their mailing list yes they have plans to uplift.
Until then we will continue offering Nemo 4.0.6 via our backports ppa.