I think its a bit early to be saying the title race is over. If you were looking at 07/08 United defence then maybe but currently we are dependant on scoring against any decent team we have conceded, very easy to drop points like that.
As has been said, if City were going to walk it, this season would be it. United very weak at the back, injuries and lack of form on the wings, weak in the centre. Not sure you will see another Fergie team with so many holes. I don't think there will be many season were United, Chelsea, Arsenal and Pool are all so weak.
As for Manicini losing his job, if the squads were swapped how do you think the league would look with SAF managing your team? I think you would be looking at an Invincible's season. But who is going to replace him and keep that team in check?