Re: The Avengers 2! The Official News and Speculation Thread - Upgrade section 5 -
We didn't find out about Gwyneth Paltrow in The Avengers until well after filming was done. It was only that Japanese trailer that revealed her scene, but before that we had no idea whether she would be in or not.
It would likely be a cameo anyway, so it's not like she's one of the major stars. There's plenty of time for her to get the call. Even with Thor: TDW, there were reshoots of Loki after filming had finished. So no need even for Paltrow to conclude she isn't in it.
Anne Hathaway: "You did not just ask me that!! What a forward young man you are!!! My goodness!!"