Idk how much of the game was made that far back so im gonna explained it very simple, the game is divided by acts (currently there are 3 acts) the first one is completed so you won´t lose any future content, act 2 is basically 95% completed ( Just missing a economy rework and some little things, that will we added when the game is close to finishing) so you can basically play it without needing to worry about content (Just that very small content missing). As you don´t want to miss much content i recommend you waiting for act 3 to be completed as arcadean is currently working on it.
The updates are released every week with some expections. (Sorry if there is some mispelling here and there or some things that aren´t well expresed, i´m not a native english speaker)