The farm is the one of the closest things WoW has to player housing; it's an adaptive environment based on your progress in the game (namely Tiller reputation), and it provides actual benefits that help (or are downright needed) to advance in the end game. Adding a way to rest on the farm would solidify this area as a central location in WoW. And while it's not a substitute for full scale player housing, it's certainly a step in some player-made persistent world (if only persistent to the player himself).
Personally, I hope we're able to fall asleep on a hammock. It's the ideal farm rest option.
Standard Disclaimer: None of this is for sure, and it's just the blues talking about what they're thinking about doing in patch 5.2.