My perception is GT is never really at E3; mostly TGS and/or Gamescom. However, I have no data to back up that perception, lol.
[edit] by "at E3" I mean presentations, announcements, reveals, etc. GT usually has some presence (playable demos, etc)
GT3 was at E3 2001, I was there personally, it was amazing.
GT4: Prologue was announced and played at PS Experience London in 2004 IIRC
GT4 was announced at E3 as well IIRC
GT Vision was premiered at E3 (or was it TGS??)
GT:HD (2006 micro transaction version that included bikes, scrapped later in 2006) was mentioned and made playable on E3 2006 IIRC
GT5 was officially announced on E3 2010 for November release by SCEA, to be pushed for December, in one of the greatest IP meltdowns considering delay IIRC
Some dreams will become reality though.
This thread will continue to live.
* too much IIRC here, Snake, please correct all my misuses