One thing I'm really curious about is how they'll do Iron Man 2 if he becomes an avenger. I mean, no offense to Marvel or anything but most of the Avengers are pretty dumb characters (*cough* Giant Man *cough*) or heroes that have powers that are wayyyyy over the top (Thor).
Part of the reason I loved this movie so much was how different it was from the other Marvel movies. It was a breath of fresh away from the over-the-top super powers like Spider Man or X-Men. Now I loved both of those movies too but it was good to see something different where everything had a technological explanation.
I think it'd really hurt an Iron Man sequel if norse gods started showing up.