yes, that's how it is in football, anything is still possible but right now the pressure is on the Liverpool team and also PSG because they have qualified for the round of 16 as runners up which means they will face the group winners in the last 16.
it is true that whoever the opponent will face in the round of 16 does not rule out the possibility for any team to be able to go further, but if you are dealing with a team of quality and have a strong mentality on the European stage like Real Madrid of course it will be very troublesome and make chances of getting through to the next round will be smaller.
PSG and Liverpool have huge pressure with strong opponent team at 16 round because finished at 2nd standing whether want or not have to faced with group winner like Manchester City, Madrid, Napoli and Bayern Munich. Except with Liverpool will not faced winner group stage at 16 round with the same country team like Tottenham Hotspur, Chelsea and Manchester City. But PSG have bigger warning because last season have to faced with Real Madrid and bad memorize after Madrid come back on second leg.
I won't with PSG not eliminated early and next round better facing with Napoli maybe if lucky on drawing schedule held on next tomorrow days, still have Napoli, Spur and Porto are group winner have possibility become opponent for PSG on 16 round.
I don't know, they could face some great teams of course, just like how PSG faced Real last year, thats a possibility. But they could face porto, Tottenham, Chelsea, Napoli, benfica as well. These are not horrible teams of course, they are teams that finished the group stages as winners, but they are not as good as Bayern, City, Real neither we have to accept that.
It means if PSG or Liverpool faces these teams, there is a good chance that they could go to quarter finals easier, or if they face the harder ones then it will be like an "early finals" feeling, specially when PSG meets these big names it becomes very crucial because winner may end up getting the title just like last year.