Thanks, do I need to explicitly merge this in or perform any actions now? Also, is there an estimated date for the next 4.0.0 (non pre)release so I can start to use this?

No, nothing specific for you to do; It'll get merged manually (by Nick).
The minute it does get merged, there's an associated -dev build on nuget (and in general authors validate those by dogfooding).
After that, there's a promotion from dev to master that triggers the full release. (In practice, lots of consumers use the -dev releases so the actual move to a non -dev release is typically a non-event)

Thanks, it looks like 3.1.1 was 5 months ago, and the first dev build of 4.0.0 was 2 months ago, so hopefully a non-dev 4.0.0 build is close by. Happy to confirm the dev ver works locally, but I might get a few side eyes pushing in a dependency to a dev version into our code base :)