my ideas:
1.notch should put old abandon buildings randomly generated like arena's and old houses and over buildings and put monster spawners in them and you must find the chest for diamond or somthing like that :)

2.I think its about time we have more weapon's like a spear you throw it and it does alot of damage to mobs.

3.there should be monkeys you know like monkeys spawn in trees and when you kill one you get an banana and monkeys will move real fast and jump high to over trees and can go up wood into the trees.

4.notch should add gold coin's and you get them from killing mobs like enemy mobs.So somtimes you kill a enemy mob you get some gold :) and there should be random generated shop's with a shop keeper in them and there should be shops in the NPC's town's.

5.There should be normal dragon's in the normal world that you can tam and fly on :3

Say what you want in 1.9 in the comment's below :D