PSG will surely to have other Champions League finals if their owner don't give up and their finance will still be supported by big corporations, foundations behind. Although, we can not say the owner from Quatar will keep owning this club forever or will keep support the club with huge budget forever, I believe in next 5 years, they will still be in Paris and 5 years with top level players are enough to have another Champions League final.
They will sooner or later harvest sweet result like Chelsea. The first will be hard and challenging but then when they already have tradition and confidence, other titles will knock their club's Hall of fame naturally.
The big investment of the owners and other companies behind PSG is not just because they want to get a title, be it a domestic title or the Champions League. There must be other income they expect from their investment such as sales of T-shirts, tickets and broadcasting rights so that their balance sheet is always guaranteed. I'm sure PSG will win the Champions League title in the near future once the team is in the hands of the right coach or they will be lucky enough with Pochettino this season if they reach the final. But Real Madrid is not an easy opponent to beat in the round of 16.
So far PSG and Manchester City are very hungry for the title of Champion League, but both failed in the final despite performing well throughout the season. The final match is not as easy as expected where there are times when the favorite team also loses surprisingly and that has happened many times in a long time. So, while PSG are still in the last 16 then they still have a chance to do so this season.