This is the first time that Beverly appears on the show without sharing a scene with Leonard, the first time that she appears in Penny's apartment, and the first time she has a conversation with Amy and Bernadette.
The "new Avengers movie" that the guys are waiting in line for is Captain America: Civil War (2016). Technically it isn't an Avengers movie, although it was nicknamed "Avengers: Part 2.5" by the fans since all regular Avengers characters were in it, except for Thor and the Hulk. The Q&A session with Joss Whedon is a bit strange since Whedon had no affiliation with this movie (although he did direct the previous Avenger movie, Avengers: Age of Ultron (2015), that Sheldon has some questions about). ETA: Q and A sessions typically take place several months or a year after a movie has been released, therefore the gang is waiting to discuss Avengers: Age of Ultron, which released a year earlier.
This episode was taped on April 19, 2016.