What if nobody unified Japan in the Sengoku period?

Hi there! First post here, please tell me if I unknowingly break any unwritten rules!

To the question:
What if, not Ieyasu, not Hideyoshi, and not Nobunaga, nobody, no warlord emerged as the dominant force after the Japanese warring states period? What if none of them acquired enough of an advantage to convert into an ultimate victory in the battle for hegemony?

Would it merely be a delay of the inevitable? Would Japan end up unified anyway in the face of external pressures (e.g. Black Ships)? Or would a different fate be in store for Japan, such as opportunistic colonization by China or America or something?

If Japan were not unified during the Sengoku period, would it be a prolonged state of violence, or would it be a tense and uneasy stalemate until whatever form of centralized Japanese government comes into being for the timeline?

Would a Japan that did not unify in the Sengoku be more or less isolationist than Edo period Japan as we know it? Would it be a case by case thing for each territory depending on each of daimyo’s policies, or might a national policy against foreign interference be mutually agreed upon?

Please give me your thoughts on matter! Thank you in advance for answering!