Touching upon the Way of the Four Elements monk subclass, Pechenin mentioned that they've"tweaked the Ki economy a little bit at higher levels to make sure that you never run out of juice as a monk", which has huge benefits for the Way of the Four Elements subclass specifically.
In concept, it rules—allowing you to blend elemental strikes with martial arts like you've just strolled out of Avatar: The Last Airbender. It achieves this by giving monks access to"Disciplines", which allow the monk to use its class resource—ki points—to cast flavourful spells. For example, the"Clench of the North Wind" discipline lets you burn ki points to cast Hold Person and bind a target in place.
The second reason is that these pseudo-spells cost way too many ki points. The Way of Shadow lets you spend a breezy two points to cast powerful utility spells like Pass Without Trace or Silence, and the Way of the Open Hand lets you try to push people around, knock them prone, or remove your enemies' ability to take reactions for a whole turn—all for free, as long as you spend ki points to use"Flurry of Blows", which Monks do a ton anyway.
The interview also covered a few other juicy details: Druid's wild shape has been tinkered with to ensure it scales well into the late game. It's a similar story with the Beastmaster Ranger, whose pets grow in strength and even appearance.