My interpretation of this is that Stobart Group, (as owners of Stobart Air and SEN airport) were looking to sell Stobart Air to Cityjet. Based on this happening, Cityjet announced and expansion from SEN.
With the buyout of Stobart Air discontinued, Stobart Air will launch the expanded operations from SEN themselves by using their Flybe franchise. There is nothing at the moment to suggest that Flybe Embraer or Q400's will operate any of these services. It looks likes this will be an expanded ATR operation but possibly, they need jet aircraft too to support some of the routes. I guess it depends on what's the routes announced will be.