This is a really excellent question that I hope gets some proper answering. At first blush, I'd say that he was just a normal dude who got mixed up in some bad time-travel mojo, but perhaps not. Does anyone care to load up a saved game and travel back to Red Mountain to have a chat with everyone's favorite carcinogenic villain? Its possible that his dialog might have some valuable hints.
I've http://www.gamesas.com/index.php?/topic/855475-when-dead-gods-dream/ before regarding Ur. At the very least I think the main thing that changes here is a possible interpretation of
"dream-sleeved inversion", which possibly gets an added connotation of a backwards flow of time (explaining exactly why he is experiencing the dreamsleeve reverse-styled).
At the most the symbolism of Lorkhan is littered all over Dagoth Ur. If Lorkhan has new look in the next world I don't think there's any more likely candidate (that we know of). If not Lorkhan then Magnus, with Nerevar filling the role of missing god.
The Triunes mantled the Divine destinies of the ‘Anticipations’ not the Princes themselves. If the Kalpa doesn't turn then those destinies cannot occur. Lorkhan's heart links to at least the next Kalpa perhaps them all (because he's outside of time?) and is what enabled Almsivi (via Dwemer tools) to ascend. Maybe the Land God forms we've seen are akin to the Mannimarco / God of Worms division.
I'd slightly change the wording of that first sentence, to "The Triunes
are the Divine destinies of the Anticipations."
This true for all poets, they arrive before their time.
And what of Alma and Seht?
Peryite and Malacath are supposed to be ascended mortals, according to this new lore.
There is a small chance he could have been referring to Trinimac as separate from Malacath (since some lore post-Oblivion suggests them being two different individuals). The context doesn't seem to suggest this but it still a consideration.