Well, you did watched the final scene (excluding the wedding scene) where all of the souls destroyed in pieces (Noctis, Ardyn, the Kings too after they hit Ardyn), and the fact is The Ring of Lucii already destroyed, there is no other way to summon The Lucian Kings again.
Maybe I put it in a wrong way, consuming soul = draining life force, sorry for the confusion, but it's a fact that Noctis died at the end of story, whether his soul destroyed or not, both Lunafreya and Noctis were finally rested in peace --> the clear interpretation, am I right? It's written and said everywhere on the story, The True King must sacrifice his life to end the Starscourge blablah so on,.. the vague one is the fates of his comrades, the fate of Noctis and Lunafreya are clear in my opinion.
Did you watched the Kingsglaive? Nyx puts on the Ring of the Lucii and is granted its power in exchange for his life, and even Noctis initially reluctant to wear the Ring, because he knows the side-effect, and it will eventually leads him to his demise