I think keeping Ike says the Steelers still want to win now. Lewis had one decent season after looking horrible up until that point. So maybe the Steelers think he'll be eaten alive covering #1 WRs. Lewis surprised me. I thought he might actually get cut last season.
Long term, Cortez is the best corner on the team hands down. And maybe the Steelers want to keep Ike so they can bring along Cortez slowly. CBs a position about confidence, so I see no problem giving Cortez a runway to confidence. And who better to learn from. Ike may have the worst hands and ball awareness, but he covers as well as anyone and is probably the best tackling corner in the game.
Plus the Steelers have a leadership problem. And Ike's one of the best guys on the team. I know a lot of guys work hard, but I suspect Ike's the real hardest working player on the team. He always shows up in mid season form to start training camp. And he's always inviting other guys to work out with him. If he could get Woodley, Dwyer, etc working out with him, we'd be golden.