Beat by Marvel in that one, two things he will play villain but not main one, Crossbones still main
— Justin Kroll (@krolljvar) November 14, 2014
Makes sense, Grillo acquitted himself well in The Winter Soldier, and Crossbones is a pretty great bad guy in the comics, particularly playing a central role in the death of Captain America during Ed Brubaker's seminal run.
On that subject, Deadline is keeping the "Russo Bros. will take over the Avengers after Whedon leaves" rumors alive by reporting that they are still likely to tackle The Infinity War two-parter after Whedon's contract expires. I'm sure after Whedon racks up big box office dollars next year, he'll want to do something of his own, and while I think James Gunn would be a better choice to take over The Avengers franchise, Joe and Anthony Russo are clearly being primed by the studio for bigger things.