I would definitely say the second alternative. I don't believe in any conscious after-life and I don't see any reason why you would have to believe in one either after reading The Gathas. The importance of the after-life was an Egyptian rather than an Indo-European idea. Zoroastrians disposed their dead towards recycling (feeding the corpses to vultures) and did not build pyramids like the Egyptians. Zarathushtra's own approach towards any ideas of an after-life seems to have be an ethical obsession with the here and now instead of the future. That which to him was unknown remained unknown. Immortality here is therefore not immortality in any Judeo-Christian-Muslim sense but rather approaching the transcendental quality of The Divine as outside the limitations of time and space. What is eternally valid? That's the question which Zarathushtra was concerned with.
Are immortals refering to life after death or is it refering to the suspension of time from being in the present without identifying to the future or past? (As in we are immortal in the present.)