Some key points

New starter decks are coming with this update. They want to introduce more faction aspects and mechanics, making them stronger at the same time.
Stratagems will receive a huge rework, as developers want to make the stratagem choice more variable.
Some old cards will become Location cards with slightly different abilities.
Improvements to leader abilities are coming, but devs don't want to change them fundamentally. More charges – more flexability.
They're not ready for Stockpile change yet
The Expansion release date is yet to be confirmed, but it's going to happen in the beginning of June. It will deliver 26 new cards packaged as an expansion.
The title for the expansion is "Price of Power" and it will contain three card drops. Every card-drop will have its own little story that fits the Price of Power. Every part will have an own reveal campaign and cinematic-trailer.

According to the devs, ST will stay pretty much the same
Weather synergy is back, this time with Fog for MO. (Dagon hype!!!)
NR is the faction that receives the "Switching-up"
The triptych arts are back, specifically the "Poor Fucking Infantry" one
The Journey reveal starts 3 days before this season ends, so watch out! (Okay, we're still acting like it's not Triss)