This is what I would like to see.
1) The Dark Sun races as they were in 2e. Elven runners, Mul, Half-Giants, etc. No new races, especially Dragonborn. The only dragons should be the ones that rule the place.
2) I'd like Tyr to be free. It's a rough and tumble world, so it's nice to have one bastion of "freedom" somewhere for the PCs to go.
3) A Templar Cleric subclass and Elemental Druid Subclass.
4) Dark Sun Monsters.
5) Lore, since it can't be assumed that people will have access to the 2e stuff.