Does anyone know when 4.12 will be released??
It’ll be soon. No official date has been announced yet. just like all other releases in the event something gets delayed. Expect a few more preview releases though before the final release happens. 
From the state of the last preview release, I’m going to stab in the dark and say it’s a good few months before it can even be considered “near-release” state. I only needed to start the engine and try placing a mesh before I discovered a dealbreaking bug which prevented any progress.
im going to take Tims answer as he actually works at epic and has the inside scoop on the state of the engine, but thanks for the input none the less
For future reference, you, or anyone else for that matter, can track the closeness to release by checking how many major issues open on the github repo for the 4.12 (or the current preview at any given time) branch.