i never really got that it was 'an avengers trailer' either. maybe it did seem like it a bit since it had Widow AND War Machine in, but since WM didn't appear in Avengers, it's even less like one now.
For me War Machine was Iron Man 2's own plot/thing
Bringing in Nick Fury and Black Widow was to drum up Avengers talk.
Now if the general audience never watched the end credits of Iron Man 1 with Nick Fury then some of Iron Man 2 wouldn't make sense.
Tony Stark is sitting in the donut
Some guy with an eye patch is asking him to join some sort of "boy band"