The Electronic Entertainment Expo, better known as E3, is a major event in the gaming calender. Held at the L.A. Convention Centre, due to it’s U.S. origin football (soccer) games rarely get a showing. The consensus tends to be that Gamscom (previously Leipzig) is the best time to show them.
PES 2010 can be seen on the game lineup list of E3 here
The E3 takes place in L.A. from 2nd of June to 4th of June.
According to various net roumors we will see the first PES 2010 video footage there. It would make sense as that would be 2 month earlier than in 2008 (first 2009 trailer was released on August 1st), while the first image this year was released 2 month earlier than last year (April 2009/ June 2008)