PSG can still win but they have to score two goals minimum. Not impossible:)
Of course, the tie isn't decided just yet, but City would love the position they are in at the moment, PSG will have to stop City from scoring at the Etihad if they are to have a chance of going through, but it's pretty difficult to stop City from scoring, they have so much quality in their side, and they are always in pole position to outscore any team they face.
In football with 2 legs, we have seen too often in many recent years that even 4 goals is not impossible to overturn. Barcelona did it many times, and of course themselves were victims. Remember PSG was a victim of it and even City themselves will remember how my team turned everything around in second leg:)
But yes, City is enjoying this position and the red card for PSG means they have a weaker side fielded.