From now on, you should mostly see bugs being fixed. In addition to that, pre-releases don't follow the regular snapshot cadence of releasing on Wednesdays, so keep an eye out!
That being said, this pre-release introduces biome blending, which means that you should no longer find harsh borders between new and old terrain. On top of that, we've also reintroduced the Amplified and Large Biome world types.
Happy mining!
Changes in 1.18 Pre-Release 1
Amplified and Large biome worlds have been adapted to the new terrain and are now once again available in the Create World screen
Removed world types "Caves" and "Floating islands" from the world creation screen
The transition between new and old terrain is less "cliffy"
Will surface height blend? Yes
Will biomes blend? Yes
Will caves blend? Your mileage may vary
Technical changes in 1.18 Pre-Release 1
--report option in data generator now creates full worldgen reference files instead of just biomes
Fixed bugs in 1.18 Pre-Release 1
MC-46584 Clicking and dragging MOUSE3 (Mouse wheel) over item slots incorrectly attempts to place full stacks in survival
MC-53444 You can get outside of the worldborder by mounting a rideable entity (boat, pig, etc.) outside of it
MC-54119 Can place/take water/lava/lilypads outside worldborder and inside spawn protection
MC-62550 Worldborder not correctly initialized for the End and Nether
MC-96535 Ambient property of potion effects with ShowParticles:0b is not disregarded
MC-113425 Player can interact with entities outside the worldborder
MC-117800 Half bed can be placed outside the worldborder
MC-121997 Every dimension's world border is operating independently, and doesn't appear where it actually is
MC-131808 Forests don't spawn trees near the positive edges, but overstretch bounds on the negative edges
MC-136523 Invisible world border in the end dimension
MC-187174 Worldborder does not take nether coordinates into account
MC-206660 Stalactites don't fall properly if there are blocks directly below it
MC-215139 Some water in caves will not start flowing
MC-219035 Fossil structures can't generate in far east and south blocks of a chunk
MC-222388 Acacia trees under y=0 often grow with bare branches