I would assume so, with all the dev's talk about "No Canned Animations" with SMART and never having control taken away from you, So stopping your character mid-mantle to hang of whatever ledge your climbing should be in the game.
I just think It would be cool to be able to slide off a ledge and be able to hang off that ledge instead of hitting the ground (If you choose too)
Like if your being chased and instead of going down to the ground (Or instead of jumping a gap) you have the choice to slide and hang off the ledge, hoping the other person keeps going.
Or to stop yourself mantling if you see an enemy and don't want to be shot while climbing up, hang there and then continue when enemy is either gone or facing away from you.