Blizzard have posted some of their future plans for World of Warcraft on the offical forums. You can flick through that here, or you may want to check out the summary 1UP have posted.

Dabiri mentions that paid character transfers -- which will allow players (for a fee) to transfer their character from one realm to another -- are "Scheduled to go live this summer, this feature will allow players to move their characters, within certain restrictions, to a realm of their choosing. This means that players will now be able to join their friends on other realms without the need to wait for a pre-set mass realm transfer." Dabiri later posts that players will be able to transfer character across accounts.