The main issue with Chelsea is their defense, the gaps are just numerous, and they lack much coordination therein. Most of them are slow and would definitely not be a match to the ever fast and swift PSG attackers. Chelsea's attack has received a good boost of J. Pedro and Delap so I presume they would keep the PSG defense busy in the match. Chelsea can only survive in that match if their defensive midfield is very fast to fall back as soon as they are beaten upfront because the defenders alone cannot bear the pressure of the PSG attackers.
IMO, the only place PSG would punish Chelsea is by outsmarting their defenders, they did it a lot to Real Madrid and they would be prepared to even do more to Chelsea. Maybe after this match, Chelsea would see the need to boost their defense. Ever since T. Silva left, Chelsea is yet to find a good replacement. I was thinking they would sign a good center back in the transfer window, but they didn't.
Even if Chelsea was good, PSG is literally "the" team to beat right now. So while yes it is true that Chelsea has some downsides, beating PSG would have been near impossible task anyways, not for Chelsea only but for every single team in the world right now. Is it completely impossible? Of course not, we have seen plenty of shocking results in world of football before and this could of course be one of them and it would be incredibly shocking to see Chelsea win, and it could happen.
But I would never bet on it, I would not put up even 1 cent on it, because to me it is clear that PSG is far superior team and will have easy time beating Chelsea too. Not even close game, I am expecting a huge margin of victory for PSG yet again.