How many members of the GA run to see a movie because of a trailer that's attached? The stories you (not you specifically) read about people going to see I Am Legend, The Simpsons, etc. just for TDK originate from these boards, or places like it. It's the fans who sometimes run to movies to see trailers, and in this case, such fans are likely already going to be seeing Green Lantern in the first place.
The reason so many, myself included, assume Potter to be the likeliest is not due to drawing in fans to watch the trailer. The exact opposite. What's the best way to put TDKR on the radar for a MASSIVE amount of people in one go? Potter. Of course, there is also the issue of having something ready in less than a month, as opposed to slightly less than two months.
As you said in your newer post, time will of course tell, but I can't see how TDKR's teaser would increase GL's numbers in any significant way. Definitely not a substantial reason to rush (if rushing is needed - again, we know next to nothing) a teaser for June.