Yes, it is most definitely still worth waiting for the next season. The spoiler of losing a character is always a harsh one, as you will now be anticipating it. However, this is not the main point the plot is driving towards. And there is still a lot to learn about titans, and the world beyond the wall.
Attack on Titan tends to cover around 30 chapters per season. Hence season 3 part 2 ended at chapter 90. And with the 30 chapter average the spoiled part will be part of the season as well considering The spoiler you received originates from
chapter 105, and can probably be expected halfway through the season.
And in the future if you do not want to be spoiled, I would recommend not going to fora and communities discussing the source material, such a for example Reddit. As the chance you will be spoiled regarding content is fairly high.