I think of Bernard more as a RB2. He will be splitting carries as they are gonna work in Hill to take Law Firms spot next year because he is due big money. Law Firm will obviously also get carries as they are likely gonna want to trade him.
Cincinnati drafting Jeremy Hill may indicate Law Firm is as good as gone. From the sounds of it, Cinci will not be making any type of decision until preseason is underway due to uncertainty of injuries at the position. At this point, though, Green-Ellis is the odd-man out. Don't be surprised if he just gets cut.
Anyway, Gio Bernard is a very, very solid No. 2 on your fantasy roster. He had 56 catches last season, most of them coming out of the backfield. This season, the Bengals envision using him in the slot, at times, which makes him viable for a pretty strong season in PPR leagues especially.
I wouldn't worry too much about Hill taking carries. Gio is in line to have a great season with the way the Bengals envision using him out of the backfield and in the slot.