I've found this article, and it made me remember an important hint from the 3rd season.
- Robb Stark: dead at the Red Wedding
- Joffrey "Baratheon": dead at the Purple Wedding
Who is the next one?
Here's a possible answer.
Meanwhile, I've finished the 1st book, A Game of Thrones, and I'm devouring the 2nd one, A Clash of Kings. The 4th season of the TV-show is currently following the second half of the 3rd book, A Storm of Swords.