Latin Tree enlargements
I am currently doing the Latin tree. I saw that it is in its "beta version". What does it mean? Does it mean that they are still going to add things? Do you get a notifications if something is added or changed? How long does it usually take for things to be added?
"Beta" is a tech term that means "in testing". So, yes they are going to add things once any remaining issues get worked out of the tree as it is now now.
You don't generally get a warning when the tree changes, but what has happened in other languages is they turn on new stuff on slowly so you'll see a gradual increase of comments along the lines of "OMG, all my gold skills are gone, I'm quitting Duolingo forever!" because new content can sometimes reset a lot of your skills.
As for how long, I have no idea. It's entirely possible that new users are even now seeing a different tree than we are (that's how it starts, with new users).