I'm not in beta, but I just previewed the (awesome!) Death Knight starter quests. I assume once they're completed, the new DKs could do the Eastern/Western Plaguelands quests easily enough and get up to 58-60...and then they have to head to Hellfire Peninsula.
Is there any kind of bridge quest there that gives the new DKs a motivation to head to Outlands? I mean, it seems like they'd be pretty focused on the Scourge. Even something as simple as the Ebon Order saying, "we want to you go to the Alliance/Horde and convince them we can be allies," then Thrall or whoever saying, "okay, we don't trust you by our side with against the Scourge. Go prove yourselves against the Legion."
If not, maybe one of you beta people could request such a transition be added.