McGreal has been down that part of the world for a few years so I'm assuming he is leaving for another job.
His appointment would make sense to a degree. Palios always like the connection Micky had with the fans and a scouser who played close to 200 games for the club may fit the bill. Combine that with experience in L2 to a decent level (ok not promotions like Micky had but took Colchester to the play offs last season), it does make sense.
If Jacko stayed on as his number 2 then I'd be happy with that. Names like Cook, Coleman, Adkins etc dont seem realistic and the likes of Fowler and Barry who arent experienced arent suitable. So McGreal would be a decent choice on paper.
That said, having read the Colchester chairmans statement, they say they felt a change in head coach after 4 years was needed. So as RLC says, it could mean nothing.