According to The Wrestling Observer, WWE's decision to turn Seth Rollins was absolutely made at the last minute, and WWE had not been toying with the idea of turning Dean Ambrose heel prior to Rollins' heel turn.
While hints had been made in the past that Ambrose would be the one to turn on the group, it's being said the notion of an Ambrose heel turn becoming a Rollins heel turn was not the case.
In related news, the subject of whether or not Seth Rollins will be getting new ring gear has been a hot topic backstage in WWE this week. The general consensus is that Rollins cannot continue wearing The Shield flack jacket and uniform, so it appears as if a change in look will be made.
It's also being reported that Seth Rollins turning on The Shield does not mean he is a technical member of Evolution, as the feeling is with Batista on hiatus, the Evolution group may no longer be around.
At this time, there are no plans to add a new member to The Shield after Rollins' departure, despite WWE teasing the idea with a new poll on their website.