Having watched currencies for a few months, it seems that any theories posited the day before an event/announcement is intended to get retail customers leaning the wrong way, thereby providing the liquidity needed for a sustained big move.
The rumor is enhanced if a sharp counter-move also takes place.
For example, today's taper talk, it's intended to draw shorts into the EUR/USD. To help the rumor, a sharp move from 1.3775 to 1.3720 took place this morning.
I'm expecting another downward move between now and Midnight EST. It'll then eventually settle between 1.3750-1.3770 until the announcement
My bet - big breakout to towards 1.39 tomorrow and a test of 1.40 by Friday.