i just want to say to anybody reading this, stop giving them ideas! if nobody has any ideas, they'll release it sooner, because they won't want to add as much before the releasse. they'll be working on for a while after the release so give them your ideas then.
your probably right, considering it would be the biggest update to minecraft since it's creation. mojang doesn't like big additions.
Especially the bosses and other mobs. They would just completely ruin it. Just look at the nether. It's so boring because there's only 2 mobs, and 3 block types which aren't too interesting in the least. so if they do add it, there would be no new mobs, maybe 1 new block, and that's about it.