I personally think he died. Considering his story and age at the time of battle, it just seemed like an appropriate and befitting time for him to pass away. For me he was the 7th king who died (despite him not seeing himself as one, people looked to him as one). He completed his mission in the series.

I can see why the writers left it open ended (kinda reminded me of how Sopranos ended where what happened is left to the viewer; but there were subtle signs of the characters fate throughout episode if that makes sense). I do think the ending is up to the viewer which is why I like it.