There will probably be another round of announcement sometime during January.
1. The big announcement for 4th Fes happened on
January, that was when they revealed the full participants and the
key visual.
2. They have not reveal any key visuals for 5th Fes yet, only silhouettes of the talents can be seen.
With all that being said, I wonder how big of a cope it is to think they might announce "additional guests", similar to how Myth and ID1 were announced as guests much later for 3rd Fes.