FFG never does just re-themes.
TI Rex is exactly like DUNE. The only change is in the board
Incorrect. They also minorly tweaked the powers of the factions, and changed the way the played cards work. The minorest of which is to remove the option to Lasgun and Shield by yourself, and the largest of which was to remove the dead cards, thus changing the Atreides analog's power in a fairly profound way. Further the change to the board is non trivial, adjusting the pacing profoundly, and changing the play dynamics as the coriolis storms from the first one effect game play in very different way. All in all, it plays different enough that I still tend to play the old version, even though I think the board and pacing are better in the first. I haven't found an elegant solution to the lack of dead cards, and dislike how..... badly it marginalizes the card bidding aspect of the game.