From the information published so far, in your opinion what Race/Class/Spec line will be a Pure Fire DPS caster? Just looking for your thoughts, thanks!

none of it would really matter and will probably change very fast by release, but: Dunmer, Dragonknight, fire spec, destruction staff.

Seconded. See http://tamrielfoundry.com/ for a list of class and weapon skill lines.

Yeh I would suggest destruction staff, there's some nice AoE abilities and passives that meet what you're after.