EA's Jeremy Dalberg has added yet another one of her "Five on Friday" Q&A features to the official Ultima Online website. Apparently the Stygian Abyss expansion pack is still headed our way, and the old 2D client will be fully supported:
"Will Stygian Abyss be accessible with the 2D client?"
I know we've answered this before, but until everyone who heard last year's version hears this year's version, it will continue to come up, so, YES! All Stygian Abyss content will be accessible by BOTH the 2D client and the new Stygian Abyss client.