Location
Shen'dralas lies in Kalimdor, between Mulgore and Desolace. Blizzard calls it a "long-hidden mystery" — a region that was there in original Azeroth without ever being enterable.
The lore threads
The name points the way. The Shen'dralar are the circle of Highborne who holed up in the ruins of Eldre'Thalas after its fall, spending millennia in Dire Maul with arcane addiction and preserved libraries. Shen'dralas picks up that thread and ties it to the centaur tribes that have held the land between Mulgore and Desolace since forever.
The zone therefore takes on two storylines Classic set up and never resolved: what became of the Highborne in Dire Maul, and what actually holds the centaur clans together.
What is deliberately left open
Of the four new regions, Shen'dralas is the one we know least about. Blizzard has given no level range. Some roundups list it as level 60 content — ⚠ that is a third-party estimate, not an official figure.
Also open: the size of the zone, the number of quests, whether it contains a dungeon, and how it relates to existing Dire Maul — whether Eldre'Thalas itself is being reworked or Shen'dralas sits beside it.
Why it is worth watching anyway
Precisely because the link to Eldre'Thalas and Dire Maul is confirmed, it looks likely that Shen'dralas leans lore zone rather than pure leveling ground. The beta starting September 17 should be the first place this gets clearer — and this page gets updated when it does.