In the past they released every three years. Now they release every year. So it is a piecemeal. But there are very strong themes active right now

- simplification for newbies (global usings, top level statements)

- better memory management for performance (ref, readonly, in, value task, custom task providers, ..)

- bring functional structures loved by many (tuples, records, pattern matching, generic math)

- code generation for aot and simplicity (code generators)

- and always productivity (many small things)

In the past we had themes about asynchronity, linq, generics (think also co/contravariance), etc.

I do once a year a training for my fellow engineers. The churn is not too big if you keep up to date once a year and start using it a bit.