I can imagine that rounding up ensemble casts for the sequel to a sleeper hit* is a tricky, and expensive business. As Red 2 comes together, Summit will be having hijinks, working out new deals with several stars of the first film, their busy schedules and sharp agents.
It would be inconceivable that they'd proceed without Bruce Willis but, equally essential in my mind, would be Mary Louise Parker and Helen Mirren.
On Mirren's part, the actress appeared on The Jonathan Ross Show last night and expressed her comittment to the role, saying:
We're doing Red 2 next year.
To the point. But contractually binding? Of course not. Still, it's the first proper indication I've seen of her involvement in the film.
Robert Schwentke, director of part one, is currently shooting R.I.P.D. It's been assumed that he'll still be busy with that when Red 2 gets going, but beyong some wish-list mumblings (Breck Eisner, for example) there's not been any indication of who might direct in Schwentke's stead.
This new film will have an entirely original storyline, drawn up by Jon and Erich Hoeber, who adapted Warren Ellis and Cully Hamner's comic for the first picture. I expect they'll have had some kind of conversation with Ellis, at least at the spitballing stage, though how involved he'd actually want to be is another question altogether.
*Well, ish. It certainly wasn't a tentpole.