I think there's a chance. The manga is full of surprises, and a new conflict that involves Thorfinn fighting could arise to add more excitement and drama to the story.
It's hard to say. The decision often depends on whether there's enough story left to tell and if there's sufficient demand from readers. Sometimes, even if there's potential, it might not happen due to various production or licensing issues.
Thorfinn does fight again. The manga develops his character through various combat situations, each presenting different obstacles and opportunities for growth.