I believe a while back, SS did indeed claim there would be an update to JB for the S2 (not specifically i777 version), so it's a good, high hope.
Throughout the history, SS does release the update, it doesn't mean AT&T users will get that update right away. AT&T has controlled the update of the firmware on all their phones.
Also, releasing an FW update, doesn't mean they will released the source code of the same time, maybe later, but not the same time, and for dev., source codes are what they need.
Official CM10.1 Nightly @ 1000MHz NOOKcolor
Offiical CM10.2 Nightly on Kindle Fire 1st-Gen
Rooted Kindle Fire HD 8.9" w/ Nova Launcher
Virgin Samsung Galaxy Tab 2 10.1"
Slimbean 8.1 on Galaxy S2 i777 - LOST
Stock ROM 4.2.2 on LG-D800