Although stranger things have happened, I don't see this one becoming a reality.
The Steelers have enough aging veterans on their roster, and Barber will be 36 in April. In other words, he's nearly as old as Steelers coach Mike Tomlin, 38.
The only role Barber could fit in Pittsburgh is catching out of the backfield on third down. Mewelde Moore is a pending free agent and may not return, but the Steelers could look for younger and/or cheaper alternatives than Barber to fill a limited role.
In my opinion, this sounds more like Barber wanting to join a contending team in Pittsburgh. If Barber could play cornerback, he would probably have a better chance.