Does the Ender Dragon egg ever hatch? [duplicate]

No, it doesn't hatch, and it doesn't act as a mob spawner. It's merely a trophy for those who figure out how to pick it up:

To obtain the dragon egg, the player may push it with a piston or place any non-solid block (like a torch) under the block the egg rests on and then destroy that block so the egg falls onto it. It is possible for the player to hit one while it is still moving to the point it breaks, however this is difficult. If broken and not collected the dragon egg will respawn some where with in "The End".

According to the Minecraft Wiki:

They currently serve no purpose, other than as a trophy or decoration.

You cannot "use" it for anything other than decoration. It does not hatch nor does it spawn another ender dragon. They are merely a trophy/decoration.

No, the Ender Dragon Egg is just a trophy for now. That might change, but as of 1.3.2 and the previews for 1.4, it doesn't do anything. The best you can do with it in 1.4 (and previews) is mount it in a nice item frame for display over your fireplace mantle.