I definitely don't think that the University of Indiana will regain its powerhouse status in the Big Ten league now that University of Wisconsin's head basketball coach Bo Ryan has retired. The retirement of Bo Ryan has nothing to do with the University of Indiana's powerhouse status, or in this case, the lack thererof.
Bo Ryan's retirement this week came as a surprise, and it may have opened the door for a new powerhouse in the Big Ten. Indiana is poised to step into the role as the team to beat in the Big Ten. Indiana boasts a great Freshmen class, in addition to a very deep and experienced roster overall.
Bo Ryan's retirement will undoubtedly have a substantial effect on the Big Ten, but it will not be an overnight change. Indiana will inevitably be a top contender, but you cannot expect to see a complete shift in power immediately simply because a coach retires. I would expect to see two or three seasons of inconsistency before one team will surface as the new "powerhouse" in the Big Ten.
A program usually needs time to regain its strength, especially after a great coach has retired. However, I think Wisconsin's coaching staff is more than able to continue their success with Bo Ryan. It's important to note MSU as a contender against Wisconsin and Indiana with its continually successful Izzo regime.