Re: Downey's last?
I really hope they don't recast Tony Stark. Have another character take Tony's place in the Avengers. I don't want to see Colin Farrell or something walk out and be like "Hey guys, its me, Tony Stark!" and have everyone squint their eyes and pretend its Robert Downey Jr.
Have Pym be the scientist on the team and have Star Lord become the badass guy who flies around in a jet pack looking awesome. Maybe have Tony Stark give the Guardians his technology or something and incorporating his suit into Star Lords. Anything but a recast.