I really believe this is a foolish question to ask since Crennel did such a bad job as the Cleveland Browns head coach he does not deserve a 2nd chance as a head coach. The only reason I am bringing this question up is because Romeo Crennel did such a good job as the Kansas City Chiefs defensive coordinator last season I do not think it is out of the question to see him getting a second chance with another team as a head coach.
Look at the Denver Broncos coaching situation when Josh McDaniels got fired. Since he drafted Tim Tebow in the first round Denver was such an unattractive head coaching gig and John Fox got a second chance after his coaching gig in Carolina. I could see Crennel getting a second chance in Jacksonville if Jack Del Rio fails to get the Jacksonville Jaguars to the postseason. This would be a major mistake by the Jaguars if they did this, but I could very easily see this happening because teams who draft quarterbacks before they search for a new coach often bring a former head coach back as a head coach. That head coach usually gets a second chance to turn a team around.
I am not going to say that this will definitely happen with Romeo Crennel. I am just saying that you cannot rule this unlikely scenario out of the question.