I'd say that can go either way. We have seen characters such as Namu leave as soon as their part was done, but we must remember that Namu was participating just for the money. Chappa participated due to his pride as a martial artist and makes it evident how important this is to him, being irked very much by Galu's stance, so it may be in his best interest to stay around and judge the skills of others. The anime does imply he left sometime before the finals with him being in his dojo not long after Tambourine killed Kuririn, though it's worth noting the anime heavily extends the time between the end of the finals and Kuririn's death.