Here is a little taste of what going to be in Minecraft in the Next Years! If you want more information please ask nicely! :)

Account System Update -

Not a game update (will not modify the game itself and will be applied regardless of the version you're playing).
The possibility to change your username and the e-mail address that is associated with your account
Global Mojang accounts are already available and can be merged with Minecraft, Scrolls and Cobalt accounts.
Once the synchronization has been made, logging into Mojang games is made by using the e-mail address instead of the username.
They might also choose this moment to implement the long-awaited online synchronization of Achievements and Statistics.
In-game usernames will be changeable, but all names on paid Minecraft accounts have to be unique (no matter if "legacy" Minecraft account or Mojang Account).
Currently being worked on by Tobias Möllstam.
It is unknown how the username change feature will be adapted to server white- and blacklists.
It is most probable that the transition to a Mojang account will become obligatory at some point.

Planned features, items, and blocks -

More sounds and music More gameplay music and sounds by C418.
More Enchantments Jeb liked the idea of having more enchantments added to the game. [citation needed]
Server Portals According to Get Satisfaction, Mojang has marked a player's suggestion of Server Portals as "Planned."
Mounting/Controlling Mobs The ability to mount and control mobs (possibly horses). Notch confirmed it was planned but will take time at Get Satisfaction. Also Jeb said on a reddit AMA in April 2012 that he "more or less promised horses to a friend."
Audio Loops Audio loops have not yet been added to the game, but may be played when the player is in a specific location (In caves, woods, sea and beside a waterfall).[citation needed]
Friends list The Minecraft documentary team of 2 Player Productions filmed a Keynote roadmap, also containing this line.
Multithreading The Minecraft documentary team of 2 Player Productions filmed a Keynote roadmap, also containing this line. Note: Minecraft is multithreaded.
Rainbow Crystalline Caves A player's suggestion of Rainbow Crystalline Caves on Get Satisfaction had been marked by Mojang as a "Planned" feature.
Dual-wielding Jeb stated that Notch is working on dual-wielding of items.
The ability to name Chests Notch has stated he will add this feature.
Zipline Mod Notch had stated that he is interested in working with the zipline mod creator to implement parts of the mod into vanilla Minecraft following MineCon. As of 5/28/12, Dinnerbone has reported that he has made string place-able, one of the components present in this mod. This, however, ended up being a new redstone component, tripwire.
Red Dragon Notch revealed during the Seecret Friday Updates(#8) that he would add dragons. One being the Ender Dragon, the other being red. Jeb informed redditors on his AMA that he would add red dragons, but was unsure exactly how.
More animals Jon Kagstrom commented on Reddit that he would like to add more animals, such as fish, birds, and tree animals, to make the game seem more 'alive.'
The Allocator Jeb stated he had considered adding a "funnel block"
Online Sync of Achievements and Statistics Notch's aim was to synchronize Achievements and Statistics online, but issues prevented this to happen. Still, there is no apparent reason for this featured to have been abandoned.
A legitimate way to obtain Sponges It has been hinted that sponges would come back as a fully functional and obtainable block in a future update[citation needed]. Although the sponge block has been available in creative mode since Beta 1.8, it is currently purely decorative. It was not added and is still not obtainable in survival mode.
Spikes or spike blocks Jeb hinted a possibility of implementing spikes that would work like pistons but push out Spikes. He later considered making a Spike Block that could be pushed by Sticky Pistons instead. Dinnerbone showed interest in adding spike blocks after adding Tripwire
Pigman User Miclee came up with the idea for Pigmen, and Notch originally planned for them to occupy NPC Villages. They are among the list of planned mobs.
Custom Paintings Notch has said that custom paintings may feature in a future update.
Snow that piles up It is unknown if this will be added but snow is already able to be at different thicknesses without using a mod. It can be obtained by using a world editor such as wordedit or mcedit.
More World Types There will be more World Types in the future, with the current ones being Default, Superflat and Large Biomes (As of Minecraft 1.3.2.)