Redstone Update

The Redstone Update is a planned major update labeled as 1.5. It was announced at MineCon 2012 at the Future Updates with the Minecraft PC Team and The Future of Mod API talks. It will probably be released sometime in January or February 2013.

Planned changes
Note: Most of the changes listed here have no detailed references since most of them were mentioned at MineCon, especially the Future Updates with the Minecraft PC Team and the The Future of Mod API talks.

You can watch the presentation here:

General
The features were:
 * Rewriting rendering engine
 * Will require a higher OpenGL feature-set
 * Will include some sort of fallback for older hardware
 * Support for high resolution textures
 * The internal layout of texture packs will change
 * Every block will have its own texture file
 * Supports the use of animated textures for all blocks
 * The geometry of individual textures can differ
 * Not intended to support HD skins
 * Much faster overall rendering, resulting in more frames per second (FPS).
 * Lighting fixes similar to the ones first introduced in snapshots 12w39a/b (during 1.4 development)
 * Support for fancy lighting control
 * Support for more realistic lighting, such as active furnaces only giving off light from their front surface
 * A new format for 1.5 texture packs (detailed on the Texture Packs page)

Gameplay

 * Redstone Improvements
 * Containers like chests and dispensers give off a redstone current that equates to how full they are
 * More predictable and consistent redstone behavior
 * The functionality of BUDs may be affected
 * Eliminating directional quirks
 * Most of the timings of redstone contraptions will change
 * Overall redstone will be more like analog signals
 * Redstone signal strength will matter (for some blocks)
 * Better Inventory management
 * Double-click items to fill the stack up as much as possible
 * Drag item stacks around to divide them up over the dragged-over slots
 * Drag item stacks around with the right mouse button to place one of that stack in each dragged-over slot, if that slot is not occupied already
 * Shift double click items in a crafting area to place all items in the inventory
 * Shift double click an item stack to move all other item stacks of that kind to that part of the inventory
 * Fixed many bugs
 * Fixed dropped anvil makes no sound when it breaks
 * Fixed linux users can't open to LAN because it's bound to 127.0.0.1
 * Fixed inconsistent pulse length/delay with torch and repeater combination
 * Fixed (Powered) redstone doesn't update right
 * Fixed clocked piston arm turns invisible when exiting game/dying/etc.
 * Fix for random black spots
 * Fix for some rendering bugs

Blocks & Items

 * Redstone Comparator
 * It is the same as a repeater, but with 2 inputs
 * If input A is stronger or equal to input B, it either repeats the signal or outputs a fresh signal
 * Output is toggleable by right clicking.
 * If input A is weaker than input B, then there is no output.
 * All containers output a redstone signal when a Redstone Comparator is placed against it directly. The strength of it depends on how full the container is
 * This works with Trapped Chests as well, meaning it can provide two redstone signals with different causes at the same time
 * Hopper
 * Places and takes out items in Hoppers, Chests, Furnaces, Minecart with Chests, Dispensers, and Brewing Stands.
 * Allows for the automation of many processes collecting the drops
 * Trapped Chest
 * Gives out a signal depending on the amount of players looking inside. 1 person = 1 strength signal, 2 people = 2, etc.
 * Crafted with a Chest and a Tripwire Hook.
 * Large Trapped Chests can be staggered with Large Chests to allow more compact storage.
 * Texture is slightly different than a normal chest, with a red stain around the latch.
 * Weighted Pressure Plate
 * Used to detect item entities
 * Gold version reaches full strength at 60 items.
 * Iron version reaches full strength at 600 items.
 * Linear, so 10 strength signal means twice as many items as a 5 strength signal.
 * Block of Redstone
 * Stores redstone dust similar to blocks of diamond, etc.
 * Emits constant redstone power
 * Works as pushable redstone power source
 * Nether Quartz
 * Is a crafting ingredient for Daylight Sensors and Redstone Comparators.
 * Can be crafted into decorative blocks.
 * Daylight Sensor
 * Outputs a signal with a strength corresponding to the intensity of the sun
 * Nether Brick (item)
 * Obtained by smelting Netherrack
 * Crafting recipe is 2x2 Nether Bricks.
 * Nether Quartz Ore
 * Drops 1 Nether Quartz item when mined, and is also effected by the fortune enchantment.
 * Block of Quartz
 * Stores Nether Quartz similar to block of diamond, etc.
 * Quartz Slab
 * Quartz Stairs
 * Chiseled Quartz Block
 * Pillar Quartz Block
 * Activator Rail
 * Minecart with TNT
 * Activated with Activator Rail
 * Minecart with Spawner 
 * Minecart with Dispenser 
 * The possibility of linking minecarts together (driven by furnace minecarts)
 * Rails to unload mobs and perhaps players when reached
 * Removed Locked Chest
 * Removed Smooth Stone Slab
 * Not to be confused with Stone Slab

World Generation

 * Nether
 * Added Nether Quartz Ore around the Nether to encourage exploration of the dimension