Bashiok hinted there are new surprises in-store for this upcoming Hallow's End. Interpret that as you will, but a brainstorm is brewing in the back of my mind -- Diablo III is likely coming out Q4 2011 with a WoW Hallow's End surprise to celebrate? Yummy ... (Speculation)
Bashiok: We update holiday events when we can. Midsummer has actually had at least one major overhaul in its history, with other tweaks and updates here and there.
Since Cataclysm changed pretty much all of the locations for towns, buildings, geography, etc. in Eastern Kingdoms and Kalimdor, that required re-placing, by hand, every banner, every fire, every decoration on every building, every quest giver, everything.
So yes it's essentially the same event with updated loot drops this year, but it was no small amount of work just to keep it the same event.
As I said we update holiday events when we can, it's not a guarantee. BUT, Hallow's End will have a few new surprises in-store.