Blizzard recently changed the Talent tree descriptions on the Death Knight page. The changes, while less descriptive, are very telling of what Blizzard plans for the Death Knight now.
Old Talent Tree Descriptions
Blood: Talents in this tree focus on damage-dealing abilities. Blood Presence increases damage output by a percentage
Frost: Talents in this tree focus on tanking abilities. Frost Presence increases threat and lowers damage taken by a percentage
Unholy: Talents in this tree have a variety of functions including summons, diseases and PvP-focused abilites. Unholy Presence increases attack speed and reduces the global cooldown on death knight abilities.
taken from World of Raids
New talent Tree Descriptions
Blood: Talents in this tree focus on weapons, armor, and strikes.
Frost: Talents in this tree focus on control, counters, and combos.
Unholy: Talents in this tree focus on spells, summons, and diseases.
The most telling difference that the new has from the old is that it seems like you could fill your role of tank or dps with any tree unlike the old where you needed to be Blood specced to tank and Frost to be dps. It seems now that the death knight just might be like a feral druid in that a change in gear and presence used could turn a DK from tank to dps or vice versa on the fly. of course this is just me speculating here. What do you think?