Realistically I think it is the right time for both Powell and Cas, he has taken them as far as he can with limited resources and to me have started to look a bit stale, he has been there 8 years which is long enough for any coach and Powell clearly has bigger aspirations.
Cas fans will be gutted, I think they know they are unlikely to get a better coach than Powell at the moment, although there are plenty of head coaches out there looking for a job. I hear from someone that used to play at the club and worked off field for a while that the board are a difficult bunch to work with...
On a separate note, Chester's deal is up at the end of the season, and Last only signed a 1 year deal, be interesting to see how long we leave it before looking at renewing his deal (I imagine the club will as long as we don't have a disastrous season).