Aasimar are now . . . Devas.

[Kobold Avenger]

But should tieflings be called asuras?

It's a name used for another type of celestial in 2e/3e that was featured in the Al-Quadim MC, Planescape: Planes of Conflict and Book of Exalted Deeds, as fiery winged talon-footed angels. They haven't been converted to 4e yet, but they have many unique abilities such as unleashing burning winds and trumpets of doom, that might mean they appear again in 4e, even if it's something like an "angel of wrath".

 

[Herobizkit]

I chose to take the assimar and all the other planetouched and lump them into the "Seraphim" race... the four elements, plus the Light (assimar) and Shadow (tiefling) energy forms.