I invest heavily on the east-side of Cincy and have been watching Madisonville for a long time. Years ago many investors started buying up Madisonville because it was thought to be up and coming. Unfortunately the neighborhood hasn't quite performed like everyone had hoped.
The area continues to get attention from investors because it is a very convenient location and surrounded by very affluent neighborhoods (Mariemont, Maderia, Indian Hill, Oakley). However, the commercial development on Red Bank Road isn't enough to spur homebuyers and quality tenants in the heart of the Madisonville neighborhoods.
A true resurgence will require a huge overhaul to the dilapidated business district along Madison Road between Stewart and Plainville. This will take many years (and millions of dollars) to accomplish.
I do believe that Madisonville is up and coming, but very, very, very slowly. That said, there are stronger investment areas in Cincinnati - OTR, Northside, and Mt Auburn.