In a few days the set of biomes will be changed and improved, with new biomes, coral reefs and bushes added.
Mgv6 biomes are hardcoded and not part of the biome API so mgv6 is unaffected.
Some biomes will be renamed, which may affect some mods.
The 'biome points' (heat point, humidity point) of the biomes are being changed, so on changeover you will get straight biome borders between existing world and newly-generated world. This is unfortunate and unavoidable and we apologise, however the biome system is not stable so there never was a guarantee of it remaining unchanged.
The terrain itself is unaffected and will be continuous over the change.
List of changes:
Add 'sandstone desert', 'cold desert', 'snowy grassland'
Rename 'glacier' biome to 'icesheet' biome
Rename non-swamp 'swamp' biomes to 'shore' biomes
Remove 'sandstone grassland' biome
Rename 'stone grassland' biome to 'grassland' biome
Edit biome points for improved similarity to Whittaker classification
Change 'tundra' to bare stone with snowblocks
Make dirt 'swamp' / 'shore' less deep
Make jungletrees spawn in slightly deeper water for larger swamps
Make dirt blob ore biome-specific, limit to dirt biomes
Make mushroom noise spread match that of appletrees as originally intended, to have mushrooms spawn in darker thicker forest areas
Add coral reefs in warm oceans
Increase heat/humidity noise spread to 1000
Add bushes and acacia bushes
Full details here https://github.com/minetest/minetest_game/pull/1022
^ Version 9
Horizontal - Temperature
Vertical - Humidity
COF Coniferous forest
DEF Deciduous forest
SGR Snowy grassland
CDE Cold desert
SDE Sandstone desert