There are a lot of lower league highly rated up and coming managers as there are a few north of the border and coaching abroad too but they don't seem to fit in Powers agenda or style of previous appointment.
Does Power have a type though?
Cooper - Was inherited i guess, but was an assistant to Hart
William - Young highly thought of coach with no management experience, played the right way.
Flitcroft - Good lower league player, turned manager with 3+ years experience. More practical football.
Brown - Old hand, lots of experience at lots of clubs
Wellens - A bit of a shot in the dark after half a season with Oldham, but a young and progressive manager playing the right way.
Sheridan - A suicidal decision to doom the club, but an old head with vast (albeit terrible) experience.
About the only type he hasn't tried is the one Swindon has had most success with over the years, the top player turned manager (DiCanio, Wise, Hoddle etc).
I don't think its possible to predict the next move at all. What is predictable is that if you are a manager with your head screwed on you dont take this job at the moment. This club is an attractive proposition in league 2 with the right conditions, as per the Wellens appointment. Thats not the case at the moment.