Going forward you should mostly see bugs being fixed. Additionally, pre-releases doesn't necessarily tend to our usual cadence of releasing on Wednesdays, so keep an eye out!
New Features in 1.16 Pre-release 1
Added new "Fabulous" graphics option - uses per-pixel blending layers for some transparent elements
Changes in 1.16 Pre-release 1
You can now milk Cows and Mooshrooms in creative mode
You can now get stew from Mooshrooms in creative mode
When you use an empty bucket on water in creative mode, you now get a bucket of water. If you have a bucket of water in your inventory already, no additional water buckets will be added when you use your empty bucket on water.
When any villager is struck by lightning, the witch it is converted to will no longer despawn
Added gamerule universalAnger (disabled by default), which makes angered neutral mobs attack any nearby player, not just the player that angered them. Works best if you disable forgiveDeadPlayers.
Added gamerule forgiveDeadPlayers (enabled by default), which makes angered neutral mobs stop being angry when the targeted player dies nearby.
Zombified piglins no longer attack innocent bystanders (unless you enable gamerule universalAnger)
Zombified piglins stop being angry if the targeted player dies nearby (unless you disable gamerule forgiveDeadPlayers)
Technical Changes in 1.16 Pre-release 1
Smithing recipes can now be added or changed through data packs
Game will now detect critical datapack issues, like missing required tags and prevent world from being loaded
Data Pack Selection
Data packs can now be selected before world is created
"Copy world" option will also copy data packs present in source world
Pack Selection Screen
Packs can now be dropped directly on data and resource pack selection screens
Dropped files and directories will be copied to appropriate places
Smithing Recipes
There's now a smithing recipe type. Recipes of this type are used in the smithing table to upgrade one item type into another type, maintaining tags.
base - Ingredient specifying an item to be upgraded.
addition - Ingredient specifying valid items to trigger the upgrade.
result - Item specifying the resulting type of the upgraded item.
Fixed Bugs in 1.16 Pre-release 1
MC-4520 Aggressive neutral mobs become neutral when the world is reloaded
MC-9856 you cannot pick up buckets of water/lava in creative mode
MC-175911 Soul Speed lasts after leaving soul blocks
MC-176041 Using a spawn egg on a strider while aiming at lava spawns both a baby and an adult strider
MC-176188 Striders are not damaged by splash or lingering water bottles
MC-176225 Accelerating a baby strider's growth does not display hand animation
MC-176470 Respawning in the nether does not de-aggro zombified piglins
MC-176637 Closing game during Mojang load screen causes NullPointerException
MC-176640 You can set your spawn point inside dangerous blocks
MC-178567 Shearing sheep does not display hand animation again
MC-178618 Feeding a flower to a brown mooshroom does not perform hand animation
MC-178961 /loot ... fish ... command no longer has any functionality
MC-179561 Retreating baby hoglins sometimes won't pathfind to the opposite direction of the player
MC-180111 Hoglins angered for reasons other than being attacked by the player ignore placed repellents.
MC-180922 Right clicking a mob with a spawn egg to spawn the baby variant doesn’t play the hand swing animation when not aiming at a block through the mob