I'm liking the new biomes, but I hope they take this as an opportunity to add some new biome-specific mobs.
That's why I like RandomMobs as it gives a sense of variety, but I do wish it could be carried over to not just mobs, but to animals as well. But yeah, more variety in the types of mobs would help. I'd love to see bears and mountain goats. Bears could be found in small caves or nooks around the world, while you'd only find mountain goats on snowy peaks that could try to headbutt the player if they got too close to them. The problem with simply adding more biomes is that it doesn't make the game any more playable. It just fragments the gameplay even more, if that makes any sense. As it is, the biomes we have now just don't have the feeling of having many uses other than being for looks, and they don't feel very dynamic. They feel empty. We have villages, why don't we have explorers that you can sometimes find while exploring that you could possibly team up with for some spelunking now that it's gotten a bit harder? Players should feel like there's a return investment with the time they put into the game.