After long speculation and silence from Blizzard's side, charms has been confirmed to be in the game during the Gameplay Panel at Blizzcon 2010.
The D3 Team had long said that charms would not return to the game, and that they didn't like the inventory space trade off that using . This has now been solved by assigning the elusive Talisman to be an exclusive "charm inventory". Charms will not yield any bonuses unless placed inside the talisman, but they can be placed outside the talisman for storage for future use.
Different Sized Charms?
Many fans have speculated about larger charms with bigger/better mods, but as of November 2011, all charms were the same 1x1 size. 
- Will stronger charms take up more space in the talisman grid? --DrHighlen
- They’re all 1x1, regardless of power. Although it would be interesting to introduce other shapes, there are no plans for it. --Diablo
Jay Wilson has specifically stated that charm affixes currently consist mainly of stat attribute bonuses, in other words, charms with strength, vitality, dexterity or willpower can at this point spawn. The complete number of affixes that can be spawned is currently unknown, however Jay Wilson mentioned during the Gameplay Panel at Blizzcon 2010 that they didn't like the extremely varying charm affixes of Diablo II.