I understand that Blizzard has the intention to make many DK specs viable for tanking, so hopefully there is one that, while perhaps being sub-optimal, will provide simplistic thread generation and a fair amount of AoE threat.

People are implying that Blizzard is trying to remedy the current lack of 5-man tanks by making most of the DK talent trees viable for tanking.. so there will probably be a blood-oriented tank spec, along with frost- and unholy-oriented ones.

Maybe all it takes is proper tanking gear, and pretty much any DK spec will work as long as you have a fair amount of healing.