Why would anyone need to guess? You can just look at Nikkei futures that trade on Globex. They are currently pointing to a 300 point drop on the open.
They don't correlate that well with where the Nikkei will close. I've seeen many times where they are down big and the Nikkei closes unchanged, or up big and the Nikkei closes flat or even down.
The nikkei tanked yesterday. It's decline today isn't so bad. It has something to do with the strength of the yen vs. the dolllar ;-)
N225 open = Prior N225 close less CME NKD contract level at about the close of US markets. Close enough. Deadly accurate, actually.
Rumors of an emergency meeting of the Fed are everywhere. Probably all BS as usual, but you gotta know the Fed is in panic mode. Bernanke is probably screaming to his cohorts...