With both Game of Thrones, Star Wars, and the MCU (at least as it's been for the last 10 years) coming to an end this year, it has that concept on my mind a lot. Endings can be very good. They can be cathartic. They can also be disappointing, or leave people wondering just what happened or with questions unanswered.
I can already guess that in each of those series I mentioned above people will be unhappy with the ending. They will be upset things didn't play out the way they expected, or wanted. They will be upset that certain characters lived or died. They will be upset that questions they felt were central to everything never ended up being touched on.
The same can happen in your game. Only, with your game you should be trying to avoid it. Game of Thrones, Star Wars, and the MCU have thousands if not millions of fans. Your game has an audience of 4-6 players, maybe a handful more.
What are the major threads in your game? Identify them, and try to tie them off. What do your players really want to see before the end, or what is it they're really hoping to do? Try to make it happen. Be ready to answer questions about things that happened or were going on.
Ultimately, the game world by the end of the campaign is no longer yours alone. It belongs to the group. It's the world their PCs adventured and lived in. It's the world they likely changed. You still have partial ownership, but there's no real reason to keep secrets from them...
Unless of course this isn't the end, and you intend to run further games in this world.