I wrote up my thoughts on the pre-release version of the
update earlier today. Now I can show you a bit of what I'm talking about.
This is me flying through the game's Nether dimension in the pre-release version of the next update. It shows the new randomly generated fort structures you'll find there, and both the new enemy types: including the cuboid magma creature that splits into baby ones when it dies. I'm playing in Creative mode so I can zoom around and give you a sense of the place - and so I don't die.
For instructions on how to play the pre-release version for yourself, see
the impressions post