Thomas Astruc and Jeremy Zag both participated in the Annecy Festival that occurred earlier today. There they said the following:
“This new season and the seasons that come after are at much more higher states and there’s much more responsibilities on the shoulders of Marinette. Let’s say that S4/S5 are the payments of everything we built within S1/S2/S3. So you’ve seen the 1st season and first act and now there is the 4th and the 5th act and obviously these acts are the most EXCITING ones because these acts are the ones where everything gets resolved. You discover all the mysteries and everything. Obviously, I won’t talk about it much because I don’t want to spoil the surprise.”
This is basically hinting that the story we know of right now will be reaching its end soon. We can expect to see the reveal and the final battle with Hawkmoth around the end of season 5. As we know, we will be getting a Season 6 and 7, so it is very likely we will see the next generation villains during that time either with or without a time skip. Obviously, this is just speculation; I’m sure we will find out more as time goes on!